Late Miocene turtles from Southern Costa Rica

Aim The closure of the Central American land-bridge connection between North and South America 3.5 million years ago was a major biogeographic event that allowed considerable interchange of the previously isolated faunas of these continents. However, the role that this connection may have had in diversification of North and South American faunas is less well understood. The goal of this study was to evaluate the potential role of the formation of this land connection in generating diversity, through repeated rare dispersal events followed by isolation. Location North and South America. Methods We evaluated the role of the Central American land-bridge connection in avian diversification using a molecular phylogeny based on four gene regions for mid-sized New World doves. Diversification events were dated using a Bayesian relaxed clock analysis and internal calibration points for endemic island taxa with known island ages. Results The reconstructed phylogenetic tree was well supported and recovered monophyly of the genera Leptotila and Zenaida, but the quail-doves (Geotrygon) were paraphyletic, falling into three separate lineages. The phylogeny indicated at least nine dispersal-driven divergence events between North and South America. There were also five dispersal events in the recent past that have not yet led to differentiation of taxa (polymorphic taxa). Main conclusions Most of these dispersal-driven diversification events occurred at the time of or after the formation of the Central American land bridge, indicating that this land connection played a role in facilitating divergence via dispersal of doves between continents.

Roles of land bridges in global biogeography and ecosystems

The Central American land bridge has served as a passageway for animals and humans moving between North and South America. Nevertheless, after the first waves of human immigration at the end of the Pleistocene, contact between the native peoples who remained on this isthmus and other peoples living in continental areas where civilization ultimately developed, is characterized, according to the field record, by the transfer of crops, technologies, and goods, until ca.1400 BP when speakers of Mesoamerican languages occupied the northwestern edge (Gran Nicoya). The ancestors of modern-day speakers of Chibchan and Chocoan languages underwent social and cultural diversification mostly within the confines of the land bridge. Some Precolumbian residents altered vegetation immediately after first arrival at least 11,000 years ago, and began to add domesticated crops to their subsistence inventory between 9000 and 7000 BP. Maize and manioc (or cassava), domesticated outside the land bridge, were introduced in Preceramic times, early in the period between 7000 and 4500 BP, and gradually dominated regional agriculture as they became more productive, and as human populations increased and spread into virgin areas. Diversity in material culture is visible ca. 6000 BP, and becomes more apparent after the introduction of pottery ca. 4500 BP. By 2000 BP culture areas with distinctive artifact inventories are discernible. Between 2500 and 1300 BP hierarchies among regions, sites, social groups, and individuals point to the establishment of chiefdoms whose elite members came to demand large numbers of costume and sumptuary goods. A few special centers with stone sculptures and low-scale architecture served a social universe larger than the chiefdom, such as clusters of recently fissioned social groups with memories of a common heritage. Social interactions on the land bridge, endowed with productive bottomlands, highland valleys, and coastal habitats, appear always to have been strongest among neighboring groups.

The Passeriformes and related avian orders (here termed “perching birds”) have presented almost insurmountable problems in resolving phylogenetic relationships. New evidence from the morphology of the avian stapes (columella) permits a reassessment of the phylogenetic relationships of the advanced perching birds. Though the stapes represents but a single character, the primitive condition for the element can be established beyond reasonable doubt as that condition found in the reptilian ancestors of birds and present in the vast majority of living birds. Therefore, where unique, derived morphologies of the stapes occur, they may be of great importance in establishing evolutionary relationships within these groups, as no other characters are presently available for which primitivederived sequences can be established beyond doubt. A cladistic approach to stapedial morphology permits a number of probable evolutionary statements concerning the “perching birds” as follows: 1) New and Old World suboscines are a monophyletic assemblage, and this group, now termed the Tyranniformes, includes the previously classified subocines of Madagascar, but not those of Australia (the lyrebirds and allies, and the New Zealand Wrens), which are shown to be oscines; 2) the wood-hoopoes and hoopoes are monophyletic and possess a unique “anvil” stapes; 3) the bee-eaters, motmots, kingfishers, and todies possess a common derived stapedial morphology and almost certainly represent a monophyletic assemblage; 4) trogons possess a stapedial morphology identical to that of the above assemblage (in 3) and are probably derived from that particular group, all of which are now termed the Alcediniformes; 5) the oscines and suboscines could not have shared a common ancestor because suboscines show a myriad of primitive characters with respect to the oscines, are relictually distributed, and yet possess a derived stapedial morphology, while the otherwise structurally advanced oscines possess the primitive condition of the stapes; for that reason the order Passeriformes is restricted to include only the oscines; 6) the Tyranniformes (suboscines) and Alcediniformes may have shared a common ancestor; both groups possess derived morphologies of the stapes that share many common features, but establishing beyond all doubt that the morphologies are strictly homologous is difficult. New evidence from the fossil record (particularly from the Western Hemisphere) provides a new basis for a paleobiogeographic analysis of "perching birds." This new evidence indicates that: 1) The Eocene of North America was a period during which structurally primitive piciform birds were the predominant, if not the only, perching birds. Eight species are now known from the Lower and Middle Eocene of North America, including one previously thought to represent a passerine. 2) The piciforms are probably New World in origin, and could have dispersed into the Old World via Beringia or across the North Atlantic. 3) The alcediniform birds are almost certainly Old World in origin; trogons, motmots, and perhaps todies crossed over into the New World using the Beringia route; alcediniforms were probably predominant during the Oligocene. 4) Suboscines are probably a Southern Continent group, and probably did not arrive into North America until relatively late, perhaps late Pliocene or early Pleistocene, when a Central American land bridge became established. 5) The Bering route probably served as a corridor for the arrival of oscines in the New World that gave rise to the New World nine-primaried oscine radiations. Apparently North America did not reciprocate to any significant degree. Oscines probably did not become established finnly in Nortli America until the Miocene and are late arrivals into Central and South America; they probably entered these regions as late as late Pliocene or early Pleistocene when the Central American land bridge became established.

The American Proteaceae are outliers from the main centres of diversity of the family in Australia and South Africa. There are about 83 species in eight genera which all belong to the monophyletic subfamily Grevilleoideae. Three genera, Embothrium, Oreocallis and Lomatia, are placed in the tribe Embothrieae (sensu Johnson and Briggs), four Euplassa, Gevuina, Panopsis and Roupala in the Macadamieae and the single genus Orites in the Oriteae. There are five genera endemic to America and three also have species in Australia and New Guinea (Gevuina, Lomatia and Orites). The Proteaceae appear to have arrived in South America via two routes. The larger genera Euplassa, Panopsis and Roupala, which are all endemic to America and have a general distribution in northern South America and south-eastern Brazil, are derived from Gondwanaland before it separated from South America. The remaining genera are distributed either in temperate South America or in the high Andes and appear to have arrived more recently via the Australia–Antarctica–South American connection. Three of these genera have species in both regions. The centres of species diversity of Euplassa, Panopsis and Roupala fall outside hypothesised forest refugia, indicating that they are not true rainforest species but species of seasonal habitats like those achieved at higher altitudes where they are commonly found. Two genera,Panopsis and Roupala, have reached Central America after the central American land bridge was formed six million years ago. The exact relationship to genera on other continents is still unclear and there is a need for a cladistic biogeographic analysis of the group based on both morphological and molecular data.

Nestled between the Cocos, Nazca, Caribbean, and South American plates, the Panama microplate represents an area of rapidly evolving tectonics throughout the past ~10 m.y. Past and current studies have observed a notable amount of seismicity throughout this region, in particular the Caribbean coast of Costa Rica, which experienced a Mw 7.7 earthquake in 1991 CE. We investigated the crust and upper mantle structure of this region using the receiver function methodology and report two results: (1) first-order lateral constraints on the position of the Panama microplate boundary near the intersection between the Central Costa Rica Deformed Belt (onshore) and North Panama Deformed Belt (offshore), and (2) an impedance contrast south and east of these belts, supporting that the Caribbean plate currently subducts beneath the Panama microplate. Observed local seismicity is a consequence of the recently (ca. 14 Ma) initiated Caribbean plate subduction beneath the overlying Panama microplate. Our results are also consistent with a doubly convergent subduction margin dominating southern Costa Rica tectonics, uplifting the Talamanca Cordillera, and causing the cessation of southern Costa Rica volcanism over the past ~10 m.y.

During the last century, the coyote (Canis latrans) has increased its distribution in Central America. Before the 1980s, it had not been recorded in Panama. New records show that coyotes have crossed the Panama Canal, indicating that continues to expand; therefore, there is a possibility that it will reach northern South America. Our objectives were to identify potential coyote colonization routes to South America, and the variables that favor its expansion. We hypothesized that habitat fragmentation benefits coyote expansion. We applied 7 algorithms to model the potential distribution of the coyote, using 196 presence records and 12 variables. The models with better performance were used to generate a consensus model. Using our consensus model and the areas with highest probability of presence, a potential colonization route was generated between Central America and northern South America. This route lies through southern Costa Rica, along the Pacific coast of Panama to the south, to the Andean mountains in northern Colombia. The variables that explained potential coyote distribution were human population density, altitude, and percentage of crops with positive influence, and tropical broadleaf forests with negative influence. These results indicate that human activities and deforestation are related to coyote distribution expansion. Actions can be implemented within the identified route to improve environmental management, in order to avoid the presence of the coyote in the ecosystems of northern South America.

Fossil palynomorphs representing 40 taxa have been recovered from lower(?) Miocene (Uscari sequence) deposits in southern Costa Rica. Three paleocommunities are suggested for the vicinity of the depositional basin—coastal mangrove (Rhizophora); some form of the lowland wet forest (Phaeoceros, Cnemideria, Bombacaceae, Alchornea, cf. Glycydendrum, cf. Banisteriopsis, Hiraea, Myrtaceae (Eugenia/Myrcia type), and Melastomataceae); and especially the midaltitude (1,000–2,000 m) cloud forest (Lycopodium, Selaginella, cf. Hymenophyllum, Lophosoria, Pityrogramma, Pteris, Podocarpus (common), Ilex, Ericaceae (Cavendishia type), and Lisiantehus). Absent are members of higher altitude communities, and vegetation of drier to arid aspect. Savannahs, important in the interchange of mammalian faunas between North and South America, remain undetected in Gulf/Caribbean Tertiary floras. Paleoenvironments are estimated as wet tropical, similar to present-day conditions, with a less diverse and insular paleophysiography accounting principally for differences between the early Miocene and modern life zones. This is in contrast to the Paraje Solo assemblage from Veracruz, Mexico, which reflects distinctly cooler climates in the late Miocene. These results are consistent with plate tectonic models for the Gulf/Caribbean region, and emerging global paleotemperature patterns derived from 18O studies of marine invertebrates.

A regional synopsis of the genus Blakea is presented that recognizes 33 species in Mexico and Central America. This summary includes a key, distributional and phenological information, notes on morphological variation, and discussions that provide rationale for relegating six binomials to synonymy. Descriptions and diagnoses are presented for four new species of Blakea (B. coloradensis, B. darcyana, and B. perforata from Panama; and B. wilsoniorum from southern Costa Rica and Panama). Analysis of the type specimens and recently collected flowering material of Topobea storkii necessitates its transfer to Blakea. Three other species (B. cuatrecasii, B. repens, and B. subconnata var. obtusa), all of which were previously known from Andean South America, are reported from Panama for the first time. Blakea, with approximately 100 species, is one of two berry-fruited genera comprising the natural neotropical tribe Blakeeae (Almeda, 1990). It is best represented in wet montane regions from southern Mexico and the West Indies to Bolivia and Brazil. Although northwestern South America is undoubtedly the center of species richness for Blakea (Wurdack, 1973), southern Central America is clearly the area of focal importance for unusual diversity in floral morphology. This floral diversity reflects adaptations to a broad array of important pollinators in the region, including rodents, buzzing bees, and hummingbirds (Almeda, 1990; Lumer, 1981; Lumer & Schoer, 1986). For a woody genus with showy, often spectacular, flowers, it is surprising that Blakea has escaped the attention of serious students until recently. The genus has not been treated in its entirety since Cogniaux's (1891) familial monograph. Even the most recent floristic treatments of the family Melastomataceae for the Mesoamerican region appeared over 30 years ago (Gleason, 1958; Standley, 1924, 1938; Standley & Williams, 1963; Winkler, 1965) when many areas were still little-explored and poorly known botanically. The account presented here is a precursor to the treatment that will appear in Flora Mesoamericana. Four new species and one new generic transfer are proposed in the context of a regional synopsis. This summary also includes a key to the 33 recognized species, distributional and phenological information, notes on variation, and discussions that provide rationale for relegating previously recognized species to synonymy.

Carnivores are extremely important in ecosystem dynamics. Coatis (Procyonidae) are a group of Neotropical species with highly developed social behavior. One coati species is the Central American or white-nosed coati (Nasua narica). This work describes the analysis of two sets of mitochondrial data for a sample of N. narica covering most of the geographic distribution range of the species. The first data set analyzed 74 specimens for three mitochondrial loci; the second, 59 specimens for complete mitochondrial genomes. Our phylogenetic analyses revealed six distinct genetic groups of N. narica in southern México, Central America, and South America, which, together with three additional groups found in northern México and southern USA in a previous study, resulted in a total of nine genetically distinct groups of N. narica. The first genetic group (G1), which began to differentiate 4.1 to 3.2 million years ago, was located on the Pacific coast of Ecuador and northern Colombia. A second genetic group (G6) was detected in northern Colombia, Panama, and southern Costa Rica, being introgressed by mitochondrial DNA from the mountain coati (Nasuella olivacea). The third genetic group (G3) was located in Costa Rica, Nicaragua, El Salvador, Honduras, and southern Guatemala. The fourth genetic group (G4) was located in north-central Guatemala and Belize. The fifth genetic group (G5) was distributed in southern México (Chiapas, Tabasco, Campeche, Quintana Roo, and Yucatán) and northern Guatemala. Finally, the sixth genetic group (G2) was found only in Mérida (Yucatán, México). Groups G2 to G5 became mitochondrially diversified over 1.9 to 1.1 million years. All groups showed high mitochondrial genetic diversity, although the South American genetic group (G1) had the highest diversity. The northern genetic groups (G4, G5) had lower genetic diversity, except for the Merida group, which is likely composed of other undetected subgroups. The existence of six (nine, considering another study) well-developed groups in N. narica is related to female phylopatry and climatic changes during the Pleistocene. A spatial autocorrelation analysis showed a very high structure, well in line with the south-to-north colonization of the American continent by N. narica.

The genome size of an organism is an important trait that has predictive values applicable to various scientific fields, including ecology. The main source of plant C-values is the Plant DNA C-values database of the Royal Botanic Gardens Kew, which currently contains 12,273 estimates. However, it covers only 2.9% of known angiosperm species and has gaps in the life form and geographic distribution of plants. Only 4.5% of C-value estimates come from researchers in Central and South America. This study provides 41 new C-values for the aroid family (Araceae), collected in the Piedras Blancas National Park area in southern Costa Rica, including terrestrial, epiphytic and aquatic life forms. Data from our study are combined with C-value entries in the RBGK database for Araceae. The analysis reveals a wider range of C-values for terrestrial aroids, consistent with other terrestrial plants, a trend toward slightly lower C-values for epiphytic forms, which is more consistent for obligate epiphytes, and comparatively low C-values for aquatic aroids.

Fossil palynomorphs representing 40 taxa have been recovered from lower(?) Miocene (Uscari sequence) deposits in southern Costa Rica. Three paleocommunities are suggested for the vicinity of the depositional basin—coastal mangrove (Rhizophora); some form of the lowland wet forest (Phaeoceros, Cnemideria, Bombacaceae, Alchornea, cf. Glycydendrum, cf. Banisteriopsis, Hiraea, Myrtaceae (Eugenia/Myrcia type), and Melastomataceae); and especially the midaltitude (1,000–2,000 m) cloud forest (Lycopodium, Selaginella, cf. Hymenophyllum, Lophosoria, Pityrogramma, Pteris, Podocarpus (common), Ilex, Ericaceae (Cavendishia type), and Lisiantehus). Absent are members of higher altitude communities, and vegetation of drier to arid aspect. Savannahs, important in the interchange of mammalian faunas between North and South America, remain undetected in Gulf/Caribbean Tertiary floras. Paleoenvironments are estimated as wet tropical, similar to present‐day conditions, with a less diverse and insular paleophysiography accounting principally for differences between the early Miocene and modern life zones. This is in contrast to the Paraje Solo assemblage from Veracruz, Mexico, which reflects distinctly cooler climates in the late Miocene. These results are consistent with plate tectonic models for the Gulf/Caribbean region, and emerging global paleotemperature patterns derived from 18O studies of marine invertebrates.

Many ecological relationships that are inherently reciprocal are often studied from one perspective only (Agrawal et al. 2007). One example is the interaction between tropical forests and nearctic-neotropical migratory songbirds (hereafter migrants). Several studies have determined that some migrant populations are limited by conditions at their tropical wintering grounds in Central America, South America and the Caribbean (Marra et al. 1998, Mills 2006); however, the ecological role of migrants in these tropical forests is poorly understood.

Coffee (Coffea arabica L. cv. Catuai) seedlings with abundant small root galls caused by an unknown root-knot nematode were found in southern Costa Rica. Morphology, esterase and malate dehydrogenase isozyme phenotypes and DNA markers differentiated this nematode from known Meloidogyne spp. A new species, M. lopezi n. sp., with common name Costa Rican root-knot nematode, is suggested. Meloidogyne lopezi n. sp. is distinguished from other coffee-associated Meloidogyne spp. by size of female lips and stylet, male body length and stylet and second-stage juvenile body and tail morphology. The region of the mitochondrial genome between COII and 16S rRNA showed a unique amplicon size of 1370 bp, and digestions with restriction enzymes HinfI, AluI, DraI and DraIII revealed characteristic PCR-RFLP patterns that differed from the tropical root-knot nematode species M. arabicida, M. incognita, M. izalcoensis, M. javanica and M. paranaensis. Characterisation of the protein-coding map-1 gene and phylogenetic analyses suggested that M. lopezi n. sp. might reproduce by mitotic parthenogenesis. Phylogenies estimated using Bayesian analyses based on the region between the COII and 16S rRNA mitochondrial genes, as well as the 18S and 28S ribosomal nuclear genes, indicated that M. lopezi n. sp. is closely related to other tropical Meloidogyne spp. that infect coffee, especially M. arabicida, M. izalcoensis and M. paranaensis from Central and South America. Isozyme analyses and PCR-RFLP of the COII-16S rRNA mitochondrial gene region enable a clear diagnostic differentiation between these species.

Following a taxonomic revision of Nectandra, a genus of about 114 species of neotropical trees, character gradients are compared against geographical distribution, habitat preferences, and reproductive phenology of individual species, with the aim of reconstructing the spatial and temporal diversification of the genus. It is shown that Nectandra, together with Ocotea, Persea, and other genera of the Lauraceae, originated from a northern hemisphere matrix that immigrated into South America, perhaps as late as after the closure of the Central American land bridge in the Pliocene. The dramatic diversification of the genus within South America was facilitated by its ornithochorous dispersal system, implying ample processes of allopatric speciation. At present, speciation seems to take place preferably by processes of ecotypic (mostly edaphic) specialization, by which widely distributed, ecologically polymorphic species give rise to swarms of ecologically narrowly specialized satellite species.