Tropical Lineages Research Articles

Going west - A subtropical lineage (Vincetoxicum, Apocynaceae: Asclepiadoideae) expanding into Europe.

Vincetoxicum sensu lato is a tropical lineage comprising two clades that have reached high northern latitudes. Of the temperate clades, one is restricted to the Far East, the other one (Vincetoxicum s. str. Clade) extends into Europe, but their ranges overlap in Central China and Japan. Three species invasive in North America, V. hirundinaria, V. nigrum and V. rossicum, are members of the Vincetoxicum s. str. Clade. We explore the prerequisites for the range expansion in the Vincetoxicum s. str. Clade performing Bayesian and Maximum Likelihood phylogenetic analyses on sequences of the nuclear internal transcribed spacer (ITS) region, the nuclear external transcribed spacer region (ETS), and five plastid markers. The resulting phylogeny is used to conduct biogeographic analysis using BioGeoBEARS to reconstruct ancestral species ranges. Moreover, we map the known occurrences of two rare characters in Asclepiadoideae, the possession of phenanthroindolizidine alkaloids and reported cases of autogamy onto our phylogeny. Finally, we have conducted ecological niche modelling using Maxent on a total of 220 spatially unique occurrences of nine Vincetoxicum s. str. species spanning more than 4,000 km along the east-west gradient to learn about the climatic conditions along the presumed migration route. Our results indicate a north-westward migration in Vincetoxicum s. str. along the Asian mountain chains to Europe. Climatic preferences of the nine species sampled are dissimilar, except for the common exposure to at least one month of subfreezing temperatures, indicating a rather wide climatic tolerance for the clade as a whole. The three species invasive in North America belong to the northern Eurasian subclade and show the rare combination of phenanthroindolizidine alkaloids and autogamy.

Infection with Ehrlichia canis and Anaplasma platys (Rickettsiales: Anaplasmataceae) in two lineages of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) from Argentina

Natural infection with Ehrlichia canis and Anaplasma platys in ticks belonging to the tropical and temperate lineages of Rhipicephalus sanguineus sensu lato from Argentina was evaluated. Samples were tested for Ehrlichia canis infection by PCR assays using 16S rRNA, dsb and p28 gene, while detection of A. platys was performed with 16S rRNA and groESL gene. The assignment of the ticks to each lineage was corroborated with 16S rDNA sequences. All ticks infected with E. canis and A. platys belonged to the tropical lineage. These results constitute the first record of E. canis infection in R. sanguineus s.l ticks from Argentina. No ticks from the temperate lineage were found to be infected with E. canis, coinciding with previous studies performed in Argentina and Uruguay where E. canis infection was not detected in R. sanguineus s.l from the temperate lineage. Because the presence of the tropical lineage of R. sanguineus s.l has been documented in tropical areas of northern Argentina between 22° and 24° of south latitude, the findings of this work indicate that transmission of E. canis and A. platys to dogs by R. sanguineus s.l probably occurs along this region.

Oligocene niche shift, Miocene diversification - cold tolerance and accelerated speciation rates in the St. John's Worts (Hypericum, Hypericaceae).

BackgroundOur aim is to understand the evolution of species-rich plant groups that shifted from tropical into cold/temperate biomes. It is well known that climate affects evolutionary processes, such as how fast species diversify, species range shifts, and species distributions. Many plant lineages may have gone extinct in the Northern Hemisphere due to Late Eocene climate cooling, while some tropical lineages may have adapted to temperate conditions and radiated; the hyper-diverse and geographically widespread genus Hypericum is one of these.ResultsTo investigate the effect of macroecological niche shifts on evolutionary success we combine historical biogeography with analyses of diversification dynamics and climatic niche shifts in a phylogenetic framework. Hypericum evolved cold tolerance c. 30 million years ago, and successfully colonized all ice-free continents, where today ~500 species exist. The other members of Hypericaceae stayed in their tropical habitats and evolved into ~120 species. We identified a 15–20 million year lag between the initial change in temperature preference in Hypericum and subsequent diversification rate shifts in the Miocene.ConclusionsContrary to the dramatic niche shift early in the evolution of Hypericum most extant species occur in temperate climates including high elevations in the tropics. These cold/temperate niches are a distinctive characteristic of Hypericum. We conclude that the initial release from an evolutionary constraint (from tropical to temperate climates) is an important novelty in Hypericum. However, the initial shift in the adaptive landscape into colder climates appears to be a precondition, and may not be directly related to increased diversification rates. Instead, subsequent events of mountain formation and further climate cooling may better explain distribution patterns and species-richness in Hypericum. These findings exemplify important macroevolutionary patterns of plant diversification during large-scale global climate change.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0359-4) contains supplementary material, which is available to authorized users.

Myrtaceae fossil leaves from the Río Turbio Formation (Middle Eocene), Santa Cruz Province, Argentina

Myrtaceae, the gum tree family, is a large angiosperm clade of 5671 species mostly distributed in tropical and subtropical regions of the world. In the southernmost tip of South America (Santa Cruz province) where the fossils analysed in this study come from (Río Turbio Formation), this family is virtually absent and the extant vegetation is largely dominated by deciduous Nothofagus pumilio and Nothofagus antarctica. During the early Paleogene, however, the Myrtaceae were an important element in southern Patagonian floras. Here, we report and describe ten taxa related to the extant genera Eugenia, Myrcia, Psidium, Myrcianthes and possible Eucalyptus and Campomanesia. The presence of a high diversity of Myrtaceae during the Eocene in one of the southernmost regions of the world could be thought as unusual. However, during this period of time (45 Ma), a number of other tropical lineages also reached these high latitudes probably as a consequence a warming climatic trend. In fact, through the Paleocene–Early Eocene interval, climatic conditions were the warmest of the Cenozoic. After this period of time, a progressive decline in temperature forced the migration of megathermal elements towards lower latitudes and, at the same time, led to the expansion of forest dominated by Nothofagus which predominate the region today.

A rich fossil record yields calibrated phylogeny for Acanthaceae (Lamiales) and evidence for marked biases in timing and directionality of intercontinental disjunctions.

More than a decade of phylogenetic research has yielded a well-sampled, strongly supported hypothesis of relationships within the large ( > 4000 species) plant family Acanthaceae. This hypothesis points to intriguing biogeographic patterns and asymmetries in sister clade diversity but, absent a time-calibrated estimate for this evolutionary history, these patterns have remained unexplored. Here, we reconstruct divergence times within Acanthaceae using fossils as calibration points and experimenting with both fossil selection and effects of invoking a maximum age prior related to the origin of Eudicots. Contrary to earlier reports of a paucity of fossils of Lamiales (an order of ∼ 23,000 species that includes Acanthaceae) and to the expectation that a largely herbaceous to soft-wooded and tropical lineage would have few fossils, we recovered 51 reports of fossil Acanthaceae. Rigorous evaluation of these for accurate identification, quality of age assessment and utility in dating yielded eight fossils judged to merit inclusion in analyses. With nearly 10 kb of DNA sequence data, we used two sets of fossils as constraints to reconstruct divergence times. We demonstrate differences in age estimates depending on fossil selection and that enforcement of maximum age priors substantially alters estimated clade ages, especially in analyses that utilize a smaller rather than larger set of fossils. Our results suggest that long-distance dispersal events explain present-day distributions better than do Gondwanan or northern land bridge hypotheses. This biogeographical conclusion is for the most part robust to alternative calibration schemes. Our data support a minimum of 13 Old World (OW) to New World (NW) dispersal events but, intriguingly, only one in the reverse direction. Eleven of these 13 were among Acanthaceae s.s., which comprises > 90% of species diversity in the family. Remarkably, if minimum age estimates approximate true history, these 11 events occurred within the last ∼ 20 myr even though Acanthaceae s.s is over 3 times as old. A simulation study confirmed that these dispersal events were significantly skewed toward the present and not simply a chance occurrence. Finally, we review reports of fossils that have been assigned to Acanthaceae that are substantially older than the lower Cretaceous estimate for Angiosperms as a whole (i.e., the general consensus that has resulted from several recent dating and fossil-based studies in plants). This is the first study to reconstruct divergence times among clades of Acanthaceae and sets the stage for comparative evolutionary research in this and related families that have until now been thought to have extremely poor fossil resources.

WHAT CAN MULTIPLE PHYLOGENIES SAY ABOUT THE LATITUDINAL DIVERSITY GRADIENT? A NEW LOOK AT THE TROPICAL CONSERVATISM, OUT OF THE TROPICS, AND DIVERSIFICATION RATE HYPOTHESES

We reviewed published phylogenies and selected 111 phylogenetic studies representing mammals, birds, insects, and flowering plants. We then mapped the latitudinal range of all taxa to test the relative importance of the tropical conservatism, out of the tropics, and diversification rate hypotheses in generating latitudinal diversity gradients. Most clades originated in the tropics, with diversity peaking in the zone of origin. Transitions of lineages between latitudinal zones occurred at 16-22% of the tree nodes. The most common type of transition was range expansions of tropical lineages to encompass also temperate latitudes. Thus, adaptation to new climatic conditions may not represent a major obstacle for many clades. These results contradict predictions of the tropical conservatism hypothesis (i.e., few clades colonizing extratropical latitudes), but support the out-of-the-tropics model (i.e., tropical originations and subsequent latitudinal range expansions). Our results suggest no difference in diversification between tropical and temperate sister lineages; thus, diversity of tropical clades was not explained by higher diversification rates in this zone. Moreover, lineages with latitudinal stasis diversified more compared to sister lineages entering a new latitudinal zone. This preserved preexisting diversity differences between latitudinal zones and can be considered a new mechanism for why diversity tends to peak in the zone of origin.

Asian origin and upslope migration of Hawaiian Artemisia (Compositae–Anthemideae)

AbstractAimMajor habitat shifts are well documented for the Hawaiian flora, but examples of shifts to the highest Hawaiian habitats by plant lineages of lowland tropical ancestry have been lacking. We sought to determine whether Hawaiian Artemisia (Compositae–Anthemideae), which includes lowland and subalpine species, represents such an example, by investigating the origin and relationships of the Hawaiian taxa.LocationHawaiian Islands and continental settings world‐wide (except Antarctica and Australia).MethodsMolecular phylogenetic analyses of Hawaiian Artemisia in the context of world‐wide diversity were conducted using nuclear and chloroplast DNA spacers. The timing of divergence events associated with inferred dispersals was estimated with calibration from fossil pollen records. Historical biogeographical analyses based on molecular trees and ecological modelling of the distributions of extant taxa were used to aid the interpretation of geographical and habitat shifts associated with diversification and long‐distance dispersal.ResultsOur findings indicate that the Hawaiian endemic species (A. australis, A. kauaiensis and A. mauiensis) constitute a clade sister to Southeast Asian A. chinensis, which, like the Hawaiian endemics, has ribbed fruit walls and, unlike other members of Artemisia except A. kauaiensis, has a distinct pappus, which is often associated with dispersal ability in Compositae. The clade encompassing A. chinensis and Hawaiian Artemisia was resolved to be most likely of Asian origin. The natural occurrence of A. chinensis in littoral habitats of Taiwan, Okinawa, and the Ryukyu and Bonin islands, and of A. australis in similar settings in the Hawaiian Islands, is likely to reflect the ancestral ecology of the Hawaiian clade, with subsequent colonization of inland, higher‐elevation habitats, including subalpine shrubland, where A. mauiensis is endemic.Main conclusionsAn ecological shift in Hawaiian Artemisia from tropical coastal habitats to drier and colder subalpine slopes is consistent with evidence from recent studies for repeated colonization of the Arctic by diverse lineages of Artemisia. Artemisia appears to be prone to such anticlimatic ecological shifts, which may explain this exceptional example of an ancestrally lowland tropical lineage in the Hawaiian high‐montane flora.

Tracing the history and biogeography of the Australian blindsnake radiation

AbstractAimWe investigated the biogeographical history of Australian blindsnakes (Ramphotyphlops) with reference to Australia's palaeoclimatic history over the past 20 Myr, particularly the development of an extensive arid zone over this period. Terrestrial vertebrate lineages dating back to the Miocene or earlier are predicted to display some or all of the following patterns: (1) for taxa including mesic, arid and monsoonal representatives, a mesic distribution should be phylogenetically ancestral; (2) mesic and monsoon tropical lineages should have diverged before the onset of aridification (with arid lineages appearing later); and (3) refuges may have allowed local persistence and diversification of lineages in the monsoon tropical and mesic zones since the mid‐Miocene.LocationContinental Australia.MethodsWe compiled a molecular data set comprising one mitochondrial and three nuclear genes for 107 individuals belonging to 28 blindsnake species. Phylogenetic relationships were reconstructed using maximum likelihood and Bayesian inference with RAxML and MrBayes, respectively. Divergence times were assessed using multidivtime. Ancestral habitat states (arid and non arid) were reconstructed using the maximum likelihood method implemented in Mesquite.ResultsThe age of the Australian Ramphotyphlops radiation was estimated at 21.9 Ma (95% credibility interval: 30.2–15.1 Ma). Mesic and monsoon tropical lineages are older than the onset of aridification, with mesic distribution appearing as ancestral on phylogenies. After the onset of aridification, lineages persisted and diversified in mesic, tropical and/or rocky refugia. Arid lineages diversified more recently (< 5 Ma).Main conclusionsAustralian blindsnakes join several other Australian squamate lineages with tropical‐mesic origins that successfully adapted to the expansion of aridity since the mid‐Miocene (c. 17 Ma) and now show evidence of multiple relatively recent evolutionary radiations across Australia. We further demonstrate that localized refugia permitted persistence and diversification of mesic taxa, with arid lineages diversifying much later (< 5 Ma) when the arid zone was well established.

Global biogeography and diversification of palms sheds light on the evolution of tropical lineages. I. Historical biogeography

AbstractAimPalms (Arecaceae/Palmae) are a model group for evolutionary studies in the tropics. Family‐wide data on taxonomy, phylogenetics and distribution are now available, but a general framework of palm evolution is still lacking. The overall aim of this study, published in two companion papers, is to seek evolutionary explanations for the geographical distribution of palm lineages and species diversity patterns at global and regional levels. In this first paper we undertake a detailed analysis of palm biogeography for all major lineages in a global context, comparing our results to the fossil record, molecular dating studies and previously established biogeographical hypotheses for the family.LocationGlobal.MethodsA dated phylogeny of all palm genera and distributional data were used to infer ancestral areas. A global model of area evolution for tropical lineages was formulated and ancestral areas were reconstructed using a maximum likelihood approach under the dispersal–extinction–cladogenesis model.ResultsThe crown node divergence of palms and divergences of all five subfamilies occurred before the end of the Cretaceous within Laurasian regions. Early range expansions into South America took place in the stem lineages of subfamilies Arecoideae and Ceroxyloideae, and into Africa and South America in Cretaceous lineages within subfamily Calamoideae. The largest subfamily Arecoideae underwent its early diversification history in South America and has been an important source of lineages expanding into other regions, notably in the major Indo‐Pacific tribe Areceae. In contrast, the history of subfamily Coryphoideae was primarily Laurasian, supporting earlier boreotropical hypotheses for the group. Dispersals across Wallace's Line are prevalent in major groups of Arecoideae, Calamoideae and Coryphoideae, both before and after the Miocene geological evolution of the Malesian Archipelago.Main conclusionsWe present the first robust biogeographical hypothesis for the evolution of palms in space and time. Although palms show evidence of dispersal limitation, our findings highlight the role of long‐distance dispersal events in the establishment of major biogeographical patterns of palm clades. This is consistent with the growing evidence for long‐distance dispersal as a major mechanism underpinning the distribution of tropical lineages.

Global biogeography and diversification of palms sheds light on the evolution of tropical lineages. II. Diversification history and origin of regional assemblages

AbstractAimPalms (Arecaceae/Palmae) are a model group for evolutionary studies in the tropics. In two companion papers, we aim to establish a general framework of palm evolution, exploring the geographical distribution of palm lineages and species diversity patterns at global and regional levels. In this, the second paper, we analyse the biogeographical events underlying regional palm assemblages and diversification processes across the family. We investigate the timing and location of diversification rate shifts and test the ‘odd man out’ pattern of low species diversity observed in the African palm flora.LocationGlobal.MethodsA complete, dated phylogeny of palm genera and ancestral area reconstructions were used to infer the biogeographical history of regional palm assemblages. Diversification rates for all genera were estimated and significant shifts in diversification rates across the family were identified under a maximum likelihood model.ResultsFollowing their early diversification in Laurasia around 100 Ma, palms dispersed southwards before the end of the Cretaceous. Few dispersal events into Africa, North America and South America were inferred, whereas numerous lineages migrated between Eurasia, the Pacific and the Indian Ocean. Thirteen diversification rate increases were identified. High diversification rates were found only in lineages from Asia, the Americas, the Pacific and the Indian Ocean, but not in any African groups. Diversification decreases were not identified in any lineage.Main conclusionsDispersal of palms into their present‐day distribution started during the Late Cretaceous, consistent with the first fossil records for rain forests in Africa and South America. The few dispersal events into South America and Africa emphasize the isolated position of these continents for most of the Cenozoic. In contrast, high dispersal between Eurasia, the Pacific and the Indian Ocean, notably during the Miocene, can be attributed to geological activity in the region, especially in Malesia. Low species diversity in Africa relative to other regions is explained here by increased in situ diversification in Asia, the Americas, the Pacific and the Indian Ocean, rather than by diversification rate decreases in Africa. This may prove to be a general pattern in other organisms showing a similar disparity in richness in Africa.

VincetoxicumandTylophora(Apocynaceae: Asclepiadoideae: Asclepiadeae)—two sides of the same medal: Independent shifts from tropical to temperate habitats

AbstractA revised phylogeny of Tylophorinae, based on 77 species of all genera presently attributed to the subtribe(Biondia, Blyttia, Diplosstigma, Goydera, Pentatropiss, Pleurostelma, Rhyncharrhena, Tylophora, Vincetoxicum)is presented. Five chloroplast markers(trnT–L,trnL–F,andpssbA–trnHintergenic spacers as well as thetrnLandtrnGintrons) and two nuclear markers (ITS, ETS) were used, totalling in 3809 base pairs. Tylophorinae are strongly monophyletic and consist of several well–defined clades. Backbone resolution between these clades is low, indicating a rapid early radiation.Pentatropissis sister to all remaining taxa, albeit with weak support; all other taxa form one big clade not corresponding to previous generic delimitations. Therefore, all genera except forPentatropissare subsumed underVincetoxicum.The early branching clades ofVincetoxicums.l. all grow in Africa, where the group originated ca. 18 Ma ago, correlating with the closure of the Tethys Ocean. The first round of differentiation took place between 12 and 15 Ma ago, resulting in Tylophorinae being distributed over almost all of their present range except for South Africa, Arabia and Europe. Two unrelated lineages of temperate, mostly erect plants hitherto named‘“Vincetoxicum”have arisen from more tropical lineages, hitherto named“Tylophora”.One clade of African species is nested inside the Australasian assemblage; this clade contains exclusively polyploid species and its re–immigration to Africa took place in the Messinian, at ca. 6.8 Ma. The EuropeanVincetoxicumspecies split from erect steppe plants of temperate Asia at ca. 4.5 Ma, coinciding with the uplift of the Tibetan plateau. This group contains two species that are presently aggressively spreading in North America after chance introductions.

The latitudinal gradient in dispersal constraints: ecological specialisation drives diversification in tropical birds

Physiological and behavioural constraints arising from ecological specialisation are proposed to limit gene flow and promote diversification in tropical lineages. In this study, we use phylogenetic analyses to test this idea in 739 Amazonian bird species. We show that patterns of species and subspecies richness are best predicted by a suite of avian specialisms common in tropical avifaunas but rare in the temperate zone. However, this only applied to niche traits associated with dispersal limitation rather than vagility. These findings are consistent with the view that diversity is promoted by more finely partitioned niches, although not simply by coevolutionary adaptation and niche packing as is often assumed. Instead, they suggest that diversification is driven by dispersal constraints, and that niches characterised by these constraints are biased towards tropical systems. We conclude that specialised tropical niches reduce the likelihood of dispersal across barriers, thereby increasing allopatric diversification and contributing to the latitudinal diversity gradient.

Interview with John C. Briggs, recipient of the 2005 Alfred Russel Wallace award

profiles ISSN 1948-6596 Interview with John C. Briggs, recipient of the 2005 Alfred Rus- sel Wallace award by Brian W. Bowen 1 Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI, USA Brian W. Bowen. Your autobiography (A Professo- rial Life, Xlibris 2009) describes conditions at eight academic institutions across seven decades. What trends did you see in academia over that time, and where are biological departments headed today? John C. Briggs. From the 1940s to the present time, research in biology departments has under- gone three major changes: from (1) problems that involved the study of whole organisms to (2) an increasing emphasis on experimental genetics, embryology, and physiology from the 1940s to the 1980s, and then (3) the rise of molecular biology from 1980 onward. But now a fourth change, an upsurge of interest in environmental biology, is having a profound effect. The course work offered in biology departments has generally followed these trends, and departmental organization has been affected to the point where some depart- ments have become split into two or three differ- ent entities. Beginning in the 1990s, biologists began to take an interest in the number of species that in- habited the world, and the fact that human altera- tion of the environment was probably eliminating many of them before they had even been de- scribed. These findings energized various private organizations and governmental agencies to the point where saving the environment and the spe- cies within it became the great conservation goal. In many institutions the environmental ethic has spread to numerous departments (law, engineer- ing, geology, social science) and it is often possible for students to major in environmental science. In biology, this has led to a new emphasis on tradi- tional studies such as morphology and systematics and a renewed appreciation for the value of natu- ral history collections. BWB. Across the timeframe of your career, what are the greatest successes in biogeography, and what is the most surprising change? JCB. During my career, the most successful inno- vation and the greatest impetus to biogeographi- cal research was the invention of phylogeography, i.e., the application of molecular methods to re- veal the genetic relationship of species and higher taxa. This advance, primarily attributable to John Avise and his students, has become an integral part of biogeography. Phylogeography has solved, and is continuing to solve, problems that have perplexed generations of biogeographers. The growth of phylogeography has been both surpris- ing and beneficial. The next most influential advance was due to the contributions of several paleontologists over recent years. They found that the generation of the earth’s latitudinal biodiversity pattern was primarily due to the continuing movement of tropical lineages toward the poles. This demon- strated that the tropics were the main fount of diversity for all latitudes. As a result, it became clear that the tropics, and particularly the high diversity centers within them, should become a first priority for conservation efforts. BWB. You witnessed the rise of cladistic biogeog- raphy, and opposed their interpretation of species distributions by strict vicariance. How would you characterize the vicariance/dispersal debate to- day? JCB. Cladistic biogeography was the result of an uneasy alliance between those who believed in cladistics, a systematic procedure, and those who were advocates of panbiogeography, formation of species by continental movement. The difficulty was that cladistics originally included the recogni- tion of dispersal as an integral part of the phyloge- netic process. But the vicarianists did not believe that biogeographic patterns could be formed by dispersal. Nevertheless, the name “cladistic bio- © 2010 the authors; journal compilation © 2010 The International Biogeography Society — frontiers of biogeography 2.3, 2010

Niche conservatism and the differences in species richness at the transition of tropical and subtropical climates in South America

Although detected long ago, latitudinal disparity in species richness lacks a consensus regarding its underlying mechanisms. We evaluated whether the main predictions derived from the tropical niche conservatism hypothesis help to explain differences regarding species richness and turnover of species and lineages between forests located in tropical and subtropical climates. If tropical niches are retained, we predict that only a subset of tropical lineages disperses and establishes outside the tropics; tip‐level phylogenetic clustering increases outside the tropics; and the climatic variation drives species richness indirectly via constraints to the distribution of lineages. We compiled 58 checklists along tropical and subtropical sites of riparian forests in southeastern South America. We tested the frequency of niches shifts for species and lineages and the abundance of taxa in each climate. Next, we checked the likelihood of pathways linking climatic and spatial predictors directly with species richness and via phylogenetic clustering estimates. Several lineages only occurred in the tropics, and the number of species and lineages that occurred in both climates was lower than expected by chance. Conversely, few lineages were exclusively subtropical and diversified in the subtropics. Phylogenetic clustering increased in subtropical sites and was correlated with decreasing species richness. An interaction between mean temperature of coldest quarter and precipitation seasonality explained most variation in species richness via increases in phylogenetic clustering. These results support an important contribution of climatic niche conservatism to explain richness disparities between tropics and subtropics, mainly because of the inability of most lineages to colonize the subtropics, which is very likely related to cold intolerance. Since niche conservatism likely drives most of the variation in tree species richness in the region, it provides a mechanistic interpretation of the observed patterns, thus fostering the understanding of richness disparities between these tropical and subtropical tree communities.

Adaptive Evolution of Leptin in Heterothermic Bats

Heterothermy (hibernation and daily torpor) is a key strategy that animals use to survive in harsh conditions and is widely employed by bats, which are found in diverse habitats and climates. Bats comprise more than 20% of all mammals and although heterothermy occurs in divergent lineages of bats, suggesting it might be an ancestral condition, its evolutionary history is complicated by complex phylogeographic patterns. Here, we use Leptin, which regulates lipid metabolism and is crucial for thermogenesis of hibernators, as molecular marker and combine physiological, molecular and biochemical analyses to explore the possible evolutionary history of heterothermy in bat. The two tropical fruit bats examined here were homeothermic; in contrast, the two tropical insectivorous bats were clearly heterothermic. Molecular evolutionary analyses of the Leptin gene revealed positive selection in the ancestors of all bats, which was maintained or further enhanced the lineages comprising mostly heterothermic species. In contrast, we found evidence of relaxed selection in homeothermic species. Biochemical assays of bat Leptin on the activity on adipocyte degradation revealed that Leptin in heterothermic bats was more lipolytic than in homeothermic bats. This shows that evolutionary sequence changes in this protein are indeed functional and support the interpretation of our physiological results and the molecular evolutionary analyses. Our combined data strongly support the hypothesis that heterothermy is the ancestral state of bats and that this involved adaptive changes in Leptin. Subsequent loss of heterothermy in some tropical lineages of bats likely was associated with range and dietary shifts.

Paleocene Malvaceae from northern South America and their biogeographical implications

The clade Bombacoideae + Malvoideae ('Malvatheca group' sensu Baum et al.) in Malvaceae comprises a mostly tropical lineage with derived taxa that now thrive in higher latitudes. The sparse fossil record, especially for Malvoideae, obscures interpretations of past distributions. We describe fossil leaves of Malvoideae from the middle-late Paleocene Cerrejón Formation in Colombia, which contains evidence for the earliest known neotropical rainforest. Fifty-six leaf compressions belonging to Malvaceae were collected from the Cerrejón Formation in northern Colombia. Leaf architectural characters were scored and optimized for 81 genera of Malvaceae. Synapomorphic characters and unique character combinations support natural affinities for the fossil leaves. Fossil pollen from the same formation was also assessed. Despite convergence of overall leaf architecture among many Malvaceae, Malvaciphyllum macondicus sp. nov. can be assigned to the clade Eumalvoideae because of distal and proximal bifurcations of the costal secondary and agrophic veins, a synapomorphy for this clade. The leaf compressions, the oldest fossils for Eumalvoideae, indicate a minimum divergence time of 58-60 Ma, older than existing estimates from molecular analyses of living species. The abundance of eumalvoid leaves and of bombacoid pollen in the midlate Paleocene of Colombia suggests that the Malvatheca group (Malvoideae + Bombacoideae) was already a common element in neotropical forests and does not support an Australasian origin for Eumalvoideae.

Molecular phylogenetic analysis of tropical freshwater mussels (Mollusca: Bivalvia: Unionoida) resolves the position of Coelatura and supports a monophyletic Unionidae

In previous molecular phylogenetic analyses of the freshwater mussel family Unionidae (Bivalvia: Unionoida), the Afrotropical genus Coelatura had been recovered in various positions, generally indicating a paraphyletic Unionidae. However that result was typically poorly supported and in conflict with morphology-based analyses. We set out to test the phylogenetic position of Coelatura by sampling tropical lineages omitted from previous studies. Forty-one partial 28S nuclear rDNA and partial COI mtDNA sequences (1130 total aligned nucleotides) were analyzed separately and in combination under both maximum parsimony and likelihood, as well as Bayesian inference. There was significant phylogenetic incongruence between the character sets (partition homogeneity test, p < 0.01), but a novel heuristic for comparing bootstrap values among character sets analyzed separately and in combination illustrated that the observed conflict was due to homoplasy rather than separate gene histories. Phylogenetic analyses robustly supported a monophyletic Unionidae, with Coelatura recovered as part of a well-supported Africa–India clade (= Parreysiinae). The implications of this result are discussed in the context of Afrotropical freshwater mussel evolution and the classification of the family Unionidae.

Phylogenetic relationships between Sophophora and Lordiphosa, with proposition of a hypothesis on the vicariant divergences of tropical lineages between the Old and New Worlds in the family Drosophilidae

Despite many studies on the phylogeny of the subgenus Sophophora, its monophyly has not been established, especially in relation to its putative relative, the genus Lordiphosa. We analyzed their phylogenetic relationships using DNA sequence data of two mitochondrial genes ( ND2 and COII) and two nuclear genes ( Adh and 28SrRNA). In constructing phylogenetic trees, we accounted for the problem of among-taxa nucleotide compositional heterogeneity, and took a sequence-partitioning approach to allow multiple substitution models for nucleotide sequences that have evolved under different evolutionary processes, particularly developing a novel, sequence-partitioning procedure for Neighbor Joining (NJ) tree construction. Trees constructed by different methods showed an almost identical and strongly supported topology in which Sophophora was paraphyletic: Lordiphosa was placed as the sister to the Neotropical Sophophora consisting of the saltans and willistoni groups, and Sophophora was divided into the clade of Lordiphosa + Neotropical Sophophora and the clade of the obscura + melanogaster groups. Based on the estimated time, 45.9 Mya, of divergence between the Old World Lordiphosa and the Neotropical Sophophora and evidence from paleontology, paleo-geography and -climatology, we propose a hypothesis that this vicariant divergence should have occurred when the North Atlantic Land Bridge between Europe and North America broke in the middle Eocene Epoch.

Why tropical forest lizards are vulnerable to climate warming

Biological impacts of climate warming are predicted to increase with latitude, paralleling increases in warming. However, the magnitude of impacts depends not only on the degree of warming but also on the number of species at risk, their physiological sensitivity to warming and their options for behavioural and physiological compensation. Lizards are useful for evaluating risks of warming because their thermal biology is well studied. We conducted macrophysiological analyses of diurnal lizards from diverse latitudes plus focal species analyses of Puerto Rican Anolis and Sphaerodactyus. Although tropical lowland lizards live in environments that are warm all year, macrophysiological analyses indicate that some tropical lineages (thermoconformers that live in forests) are active at low body temperature and are intolerant of warm temperatures. Focal species analyses show that some tropical forest lizards were already experiencing stressful body temperatures in summer when studied several decades ago. Simulations suggest that warming will not only further depress their physiological performance in summer, but will also enable warm-adapted, open-habitat competitors and predators to invade forests. Forest lizards are key components of tropical ecosystems, but appear vulnerable to the cascading physiological and ecological effects of climate warming, even though rates of tropical warming may be relatively low.

Untangling Gloxinieae (Gesneriaceae). II. Reconstructing Biogeographic Patterns and Estimating Divergence Times Among New World Continental and Island Lineages

Gesneriaceae tribe Gloxinieae is a diverse clade of approximately 19 genera and 215 species. As with many tropical lineages, patterns and timing of diversification are poorly understood. This is a particular difficulty in groups such as the Gesneriaceae that have no fossil record. Here we explore maximum likelihood and Bayesian inference of phylogenetic relationships in the tribe based on nuclear, chloroplast, and morphological data sets, use Fitch parsimony optimization (FPO) and dispersal vicariance (DIVA) analyses to explore biogeographic patterns in the Gesnerioideae, and use penalized likelihood calibrated by geological events in the Caribbean and South America to explore timing of movement of lineages among Caribbean, Central American, and South American land masses and islands. Likelihood and Bayesian analyses increase support of previous hypotheses of relationships using parsimony and provide additional resolution in some parts of the phylogeny. FPO and DIVA analyses suggest that the most likely scenario for movement among Central American, Caribbean, and South American areas was either an early dispersal to Central America and the Caribbean prior to diversification of the Gloxinieae clade with subsequent back dispersal to South America, or the ancestor of the Gloxinieae had a broad distribution across Central America and Andean/western South America. Estimations of the timing of movement of these lineages among these land masses suggests that the Greater Antilles/Aves Ridge landbridge likely played a role in dispersal events and that the Gloxinieae/Gesnerieae lineage likely arrived in the Central America/Caribbean zone at least 26 million years ago.