Biogeographic Transition Zone Research Articles

Mitochondrial lineages inNotochthamalus scabrosusas indicators of coastal recruitment and interactions

A significant genetic cline has previously been identified along the Chilean coast in the barnacle Notochthamalus scabrosus. Samples from the previous study, spanning 800 km, were not able to show whether the southern lineage ultimately goes to fixation at higher latitudes. In addition to expanding the geographic sampling of this species, locations that were sampled approximately four to five generations ago were resampled for this study, enabling a temporal comparison of the location and strength of the observed cline. Here, we show that although the cline persists as expected, the tremendous changes in observed lineage frequencies near the clinal boundary are indicative of source-sink dynamics that may be associated with a codistributed biogeographic transition zone. We also find that the southern lineage does not increase in frequency in more southern populations, suggesting that this lineage is maintained through a combination of density-dependent interactions and a coastal fitness gradient.

Local climatic drivers of changes in phenology at a boreal-temperate ecotone in eastern North America

Ecosystems in biogeographical transition zones, or ecotones, tend to be highly sensitive to climate and can provide early indications of future change. To evaluate recent climatic changes and their impacts in a boreal-temperate ecotone in eastern North America, we analyzed ice phenology records (1975–2007) for five lakes in the Adirondack Mountains of northern New York State. We observed rapidly decreasing trends of up to 21 days less ice cover, mostly due to later freeze-up and partially due to earlier break-up. To evaluate the local drivers of these lake ice changes, we modeled ice phenology based on local climate data, derived climatic predictors from the models, and evaluated trends in those predictors to determine which were responsible for observed changes in lake ice. November and December temperature and snow depth consistently predicted ice-in, and recent trends of warming and decreasing snow during these months were consistent with later ice formation. March and April temperature and snow depth consistently predicted ice-out, but the absence of trends in snow depth during these months, despite concurrent warming, resulted in much weaker trends for ice-out. Recent rates of warming in the Adirondacks are among the highest regionally, although with a different seasonality of changes (early winter > late winter) that is consistent with other lake ice records in the surrounding area. Projected future declines in snow cover could create positive feedbacks and accelerate current rates of ice loss due to warming. Climate sensitivity was greatest for the larger lakes in our study, including Wolf Lake, considered one of the most ecologically intact ‘wilderness lakes’ in eastern North America. Our study provides further evidence of climate sensitivity of the boreal-temperate ecotone of eastern North America and points to emergent conservation challenges posed by climate change in legally protected yet vulnerable landscapes like the Adirondack Park.

Mining of EST-SSR from 454 pyrosequencing in the surf clam Mesodesma donacium (Lamark, 1818)

Novel simple sequence repeats (SSR) were identified from 454 transcriptome pyrosequencing ESTs in the surf clam Mesodesma donacium. From 7,734 ESTs annotated with SSR motives, 75 putative EST-SSRs were selected according their repetitive DNA sequence and functional annotation (Gene ontology), of these, 15 were characterized on 45 individuals of two wild populations located in two different biogeographic transition zones of the coast of Chile (30 and 42°S). Most loci were in Hardy–Weinberg equilibrium, and the polymorphic information content (PIC) ranged from 0.243 to 0.634. Pairwise Fst between sampled populations was estimated in 0.478. These EST-SSR markers promise to be useful for future management strategies of this overexploited species.

Freeze Tolerance of Nine Zoysiagrass Cultivars Using Natural Cold Acclimation and Freeze Chambers

Winter-hardiness of zoysiagrass (Zoysia spp.) cultivars is an important attribute throughout the biogeographical transition zone; thus, the inability to withstand freezing temperatures may limit the use of these cultivars. The objective of this research was to determine the freeze tolerance (LT50) of nine zoysiagrass cultivars grown in Raleigh, NC. Four Zoysia japonica Steud. cultivars (JaMur, Palisades, Empire, and Ultimate) and five Zoysia matrella (L.) Merr. cultivars (Pristine, Zeon, Cavalier, Diamond, and Zorro) were chosen to undergo freeze testing. Cores were taken from the field in Feb. 2008, 2009, and 2010 for the winter trials and in Apr. 2008, 2009, and 2010 for the spring trials (after green-up had occurred). The cores were subjected to freeze treatments of –6, –8, –10, –12, and –14 °C in programmable freezers. After thawing, cores were placed in a 41/20 °C greenhouse to promote green-up. Cores were rated for green-up after 4 weeks on a 1 to 9 scale. Nonlinear regression analysis was used to calculate an LT50 value for each cultivar. ‘JaMur’, ‘Palisades’, ‘Empire’, and ‘Ultimate’ were no different in the winter trials with an LT50 ranging from –9.8 to 10.2 °C. Among the matrella species, ‘Zeon’, ‘Cavalier’, and ‘Zorro’ were no different but ‘Diamond’ (LT50 of –6.0 °C) and ‘Pristine’ (LT50 of –5.7 °C) had less tolerance to freezing than the other matrella cultivars (LT50 range from –9.7 to –9.8), suggesting lower ability to cold-acclimate in the field than the other cultivars. Shoot weights of cores were correlated to visual green-up ratings for each cultivar with an R2 range from 0.70 to 0.99 indicating a good relationship between the green-up ratings and shoot weights.

Integrative inventory of Bolivia’s lowland anurans reveals hidden diversity

Jansen, M., Bloch, R., Schulze, A. & Pfenninger, M. (2011). Integrative inventory of Bolivia’s lowland anurans reveals hidden diversity. —Zoologica Scripta, 40, 567–583.We conducted an integrative species inventory and re‐evaluated the taxonomic status of anuran populations from lowland Bolivia that we putatively ordered to 59 a priori species. The analyses of own and published data of mtDNA (16S), bioacoustics, and adult and tadpole morphology, however, revealed a total number of 69 divergent lineages. With the data at hand, the taxonomic assignment of only 27 from 69 lineages (39.1%) to nominal species was supported, the assignment of nine lineages (14.5% of 69) was attributed to incertae sedis, and another 33 divergent lineages (47.8%) could not yet be assigned to any species. Of those lineages, 16 were confirmed as divergent to other species by at least two of the following lines of evidence: high genetic divergence, strong differences in advertisement calls, morphology or ecology. These ‘confirmed genealogical lineages’ are suggested to belong to good species following standards of divergence of the group under study, many of them probably being candidates for formal descriptions. Another 17 lineages were considered as ‘unconfirmed genealogical lineages’ showing significant difference to all other described species only in one line of evidence. Within 6 of our 69 revealed lineages, we detected deep conspecific lineages. Some species in this study showed remarkable intraspecific call variation not congruent with genetic divergence. Our results suggest that many Bolivian anuran species that are assigned to supposedly ‘widespread’ South American species apparently belong to previously unrecognized lineages with supposedly smaller distribution areas. Our data on a regional scale urge for an integrative taxonomic review of these and other widespread lowland Neotropical anuran species, as many of them may actually represent species complexes. However, a complete inventory of Neotropical amphibians apparently is a far more complex challenge than previously thought, and only cooperative, supraregional and cross‐country approaches will reveal the actual amphibian diversity in the Neotropics. We postulate that Bolivia’s lowlands can be assessed as a region joining distinct regional faunal diversity and thus deserve reinforced conservation and research efforts to fulfil its unique situation as climatic and biogeographic transition zone.

Faunal changes and geographic crypticism indicate the occurrence of a biogeographic transition zone along the southern East Pacific Rise

Aim Deep-sea hydrothermal vents have now been reported along all active mid-ocean ridges and back-arc basins, but the boundaries of biogeographic entities remain questionable owing to methodological issues. Here we examine biogeographic patterns of the vent fauna along the East Pacific Rise (EPR) and determine the relative roles of regional and local factors on the distribution of biodiversity associated with mussel beds along a poorly explored zone, the southern EPR (SEPR). Location East Pacific Rise. Methods A species list of macrobenthic invertebrates along the EPR was compiled from the literature and supplemented with data recovered during the French research cruise BIOSPEEDO carried out in 2004 along the SEPR. Biogeographic patterns were assessed by combining the identification of morphological species with a molecular barcoding approach. A multivariate regression tree (MRT) analysis was performed to identify any geographic breaks, and an empirical distribution of species richness was compared with predictions provided by a mid-domain effect model. Macrofaunal community structure associated with mussel beds along the SEPR was analysed in relation to environmental factors using cluster and canonical redundancy analyses. Results Sequencing of the cytochrome c oxidase subunit I gene revealed the occurrence of several cryptic species complexes along the EPR, with the equator separating the southern and northern clades. Furthermore, during the BIOSPEEDO cruise at least 10 still unnamed species were collected between 7 degrees 25' S and 21 degrees 33' S. The shift in community structure identified by MRT analysis was located south of 17 degrees 34' S or south of 13 degrees 59' S, depending on the data used, suggesting that the southern part of the SEPR (17 degrees 25'-21 degrees 33' S) constitutes a biogeographic transition zone in the vent fauna along the EPR. At a regional scale, latitude combined with the type of venting was significantly correlated with the community structure associated with mussel beds. Main conclusions Together, the molecular data, in situ observations, and the distribution of species suggest that the high diversity of vent fauna species presently observed between 17 degrees 25' S and 21 degrees 33' S is probably a result of the overlap of several distinct biogeographic provinces. We argue that this area thus constitutes a biogeographic vent fauna transition zone along the EPR.

Underpinning global biogeographical schemes with quantitative data

Underpinning global biogeographical schemes with quantitative data

How does the connectivity between populations mediate range limits of marine invertebrates? A case study of larval dispersal between the Bay of Biscay and the English Channel (North-East Atlantic)

For many marine species, larval dispersal plays a crucial role in population persistence, re-colonization of disturbed areas, and distribution of species range limits through the control of population connectivity. Along the French Atlantic coast (NE Atlantic), a biogeographical transition zone has been reported between temperate and cold-temperate marine faunal assemblages. Hydrodynamics in this area are highly complex and variable including numerous mesoscale features (e.g. river plumes, fronts, upwellings, low salinity lenses), which could constrain larval transport and connectivity. In this context, the aim of this study was to assess how hydrodynamic conditions and biological traits influence larval transport and contribute to population connectivity along the biogeographical transition zone between the Bay of Biscay and the English Channel. A coupled bio-physical individual-based model was used at a regional scale to track larval trajectories under realistic hydroclimatic conditions (tides, river run-offs, and meteorological conditions) and for some common life-history traits. Larval particles were released monthly from February to August for the years 2001 to 2005, from 16 spawning populations corresponding to the main bays and estuaries of the study area. Two planktonic larval durations (2 vs. 4 weeks) and three vertical distributions (no swimming behaviour, diel vertical migration, and ontogenic vertical migration) were considered. Dispersal kernels were described by 17 parameters and analysed in a multivariate approach to calculate connectivity matrices and indices. The main factors responsible for the variability of the dispersal kernels were the spawning month in relation to the seasonal variations in river run-offs and wind conditions, the planktonic larval duration, the spawning population location, and the larval behaviour. No significant inter-annual variability was observed. Self-retention rates were high and larval exchanges occurred mainly within the main hydrodynamical areas: the western English Channel, the Southern Brittany, and the Central Bay of Biscay. Connectivity between the English Channel and the Bay of Biscay populations was low and occurred only under particular hydroclimatic conditions (i.e. high river run-off and strong SW winds) and for some biological traits (i.e. long planktonic larval duration).

A framework for delineating biogeographical regions based on species distributions

AbstractAim Biogeographical regionalizations, such as zoogeographical regions, floristic kingdoms or ecoregions, represent categorizations central to many basic and applied questions in biogeography, ecology, evolution and conservation. Traditionally established by experts based on qualitative evidence, the lack of transparency and quantitative support has set constraints on their utility. The recent availability of global species range maps, novel multivariate techniques and enhanced computational power now enable a quantitative scrutiny and extension of biogeographical regionalizations that will facilitate new and more rigorous uses. In this paper we develop and illustrate a methodological roadmap for species‐level biogeographical regionalizations at the global scale and apply it to mammals.Location Global.Methods We explore the relative usefulness of ordination and clustering methods and validation techniques. The performance of nine different clustering algorithms is tested at different taxonomic levels. The grain of regionalization (i.e. the number of clusters) will usually be driven by the purpose of the study, but we present several approaches that provide guidance.Results Non‐metric multidimensional scaling offers a valuable first step in identifying and illustrating biogeographical transition zones. For the clustering of regions, the nine different hierarchical clustering methods varied greatly in utility, with UPGMA (unweighted pair‐group method using arithmetic averages) agglomerative hierarchical clustering having consistently the best performance. The UPGMA approach allows a tree‐like phenetic representation of the relative distances of regions and can be applied at different levels of taxonomic resolution. We find that the new quantitative biogeographical regions exhibit both striking similarities to and differences from the classic primary geographical divisions of the world’s biota. Specifically, our results provide evidence that the Sahara, northern Africa, the Arabian Peninsula and parts of the Middle East should be regarded as part of the Afrotropics. Further, the position of the New Guinean continental shelf, Lydekker’s Line, is supported as an appropriate border to separate the Oriental and Australian regions.Main conclusions We propose that this sort of new, quantitative delineation and relationship assessment across taxonomic and geographical grains is likely to offer opportunities for more rigorous inference in historical and ecological biogeography and conservation.

The South American Biogeographic Transition Zone: An analysis from Asteraceae

AbstractIn order to elucidate the biotic diversification of Asteraceae inhabiting the South American Transition Zone, we undertook a panbiogeographic analysis (based on a parsimony analysis of endemicity) and a cladistic biogeographic analysis. The study units were the six biogeographic provinces of this zone plus the seven subregions of the Neotropical and Andean regions, considered as “outgroups”. Species analyzed belonged to the generaArnaldoa, Barnadesia, Belloa, Berroa, Chevreulia, Chuquiraga, Cuatrecasiella, Dasyphyllum, Doniophyton, Duseniella, Facellis, Fulcaldea, Gamochaetopsis, Huarpea, Hypochaeris, Jalcophila, Lucilia, Luciliocline, andSchlechtendalia. A parsimony analysis of endemicity, based on presence/absence data of the 66 individual tracks ranged on two or more areas, allowed to identify four generalized tracks: (1) Coastal Peruvian Desert and Puna provinces; (2) Central Chilean, Patagonian, and Subantarctic subregions; (3) Amazonian, Chacoan, and Parana subregions; and (4) Puna province and Parana and Chacoan subregions. The Puna and Parana provinces, connected with two different generalized tracks each, constitute nodes. A cladistic biogeographic analysis, based on the paralogy–free subtrees extracted from the taxonomic area cladograms ofBarnadesia, Chuquiraga, Dasyphyllum, Hypochaeris, and the Lucilia group, allowed obtaining a general area cladogram, which indicates a basic separation between the Atacama, Monte, and Prepuna provinces closely related to the Andean region, and the North Andean Paramo, Coastal Peruvian Desert, and Puna provinces closely related to the Neotropical region. Our results corroborate once again the transitional character of the provinces assigned to the South American Transition Zone, and allow speculating on their close affinities with the Andean and Neotropical regions.

Restricted gene flow in Chilean barnacles reflects an oceanographic and biogeographic transition zone

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 394:165-177 (2009) - DOI: https://doi.org/10.3354/meps08265 Restricted gene flow in Chilean barnacles reflects an oceanographic and biogeographic transition zone C. Zakas1, J. Binford2, S. A. Navarrete3, J. P. Wares1,* 1Department of Genetics, University of Georgia, Athens, Georgia 30602, USA 2Yale University School of Medicine, New Haven, Connecticut 06510, USA 3Estación Costera de Investigaciones Marinas & Center for Advanced Studies in Ecology and Biodiversity, Pontificia Universidad Católica de Chile, Santiago, Chile *Corresponding author. Email: jpwares@uga.edu ABSTRACT: Broad scale patterns of genetic structure in coastal communities are strongly affected by both ecological transitions and larval dispersal. Along the Chilean coast, we examined 2 species of co-distributed barnacles, Jehlius cirratus and Notochthamalus scabrosus, which span an ecological transition associated with a sharp increase in larval recruitment. A distinct break in haplotype frequencies in the mitochondrial cytochrome oxidase I (mtCOI) gene was detected in N. scabrosus, with only marginal genetic structure observed in J. cirratus, suggesting significant differences in either selective pressures or dispersal ability between the species. The nuclear gene elongation factor 1α was also analyzed in N. scabrosus, and similarly suggested limited gene flow. The sharp genetic transition is downstream of the described ecological transition, effectively mirroring a genetic cline described in a different barnacle species along the North American Pacific coast. KEY WORDS: Phylogeography · Oceanography · Intertidal · Chile · Barnacle · Upwelling · Recruitment Full text in pdf format PreviousNextCite this article as: Zakas C, Binford J, Navarrete SA, Wares JP (2009) Restricted gene flow in Chilean barnacles reflects an oceanographic and biogeographic transition zone. Mar Ecol Prog Ser 394:165-177. https://doi.org/10.3354/meps08265 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 394. Online publication date: November 18, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Phylogeographic analyses of the 30 degrees S south-east Pacific biogeographic transition zone establish the occurrence of a sharp genetic discontinuity in the kelp Lessonia nigrescens: vicariance or parapatry?

Phylogeographic studies are lacking in the Southern Hemisphere, and in particular in the south-eastern Pacific. To infer the possible scenario for the debated biogeographic transition zone located at 30-33 degrees S along the Chilean coast, we investigated whether there is a concordance between the phylogeographic pattern and the biogeographic transition in the intertidal kelp Lessonia nigrescens whose distribution is continuous across this transition zone. Using a combination of four makers located in the three genomic compartments (chloroplast, mitochondria and nucleus), we showed the presence of two main divergent lineages, possibly cryptic species. There was an exact match of the phylogeographic break with the 30 degrees S biogeographic transition zone, suggesting a common origin. The combined information given by the multilocus approach and by the population analysis suggested the occurrence of a budding speciation, with a northward range expansion.

Checklist of benthic marine algae and cyanobacteria of northern Portugal

Abstract The northern Portuguese coast is a biogeographic transition zone where many macroalgal species have their distribution limits; it is thus a particularly interesting region for investigating species distribution shifts. An updated and complete list of species for this region is not available in spite of its baseline importance for comparative studies with past and present data. Based on new records, literature references, and herbarium data, we provide an updated checklist of the benthic marine algae of the northern Portuguese coast. This checklist includes 346 species: 26 Cyanobacteria, 200 Rhodophyta, 70 Ochrophyta, and 50 Chlorophyta. From these, 21 species are new records for the Portuguese coast (Lyngbya aestuarii, Lyngbya semiplena, Microcoleus acutirostris, Myxosarcina gloeocapsoides, Aiolocolax pulchella, Antithamnion densum, Antithamnion villosum, Antithamnionella spirographidis, Dasya sessilis, Furcellaria lumbricalis, Neosiphonia harveyi, Porphyrostromium boryanum, Chorda filum, Dictyopteris ambigua, Sphacelaria rigidula, Undaria pinnatifida, Vaucheria coronata, Vaucheria velutina, Ulothrix implexa, Ulva scandinavica, and Umbraulva olivascens) and 33 were recorded for the first time in the north of Portugal. Alien species have increased in number and extended their distribution range over the last 10 years in the study area. Distribution shifts of northern cold water species with southern distribution limit in the north of Portugal were not consistent among species.

Comparative phylogeography of two coastal polychaete tubeworms in the Northeast Atlantic supports shared history and vicariant events

The historic processes which have led to the present-day patterns of genetic structure in the marine coastal fauna of the Northeast Atlantic are still poorly understood. While tectonic uplifts and changes in sea level may have caused large-scale vicariance, warmer conditions during glacial maxima may have allowed pockets of diversity to persist to a much wider extent than in the Northwestern Atlantic. The large-scale geographic distribution of deeply divergent lineages of the coastal polychaete tubeworms Pectinaria koreni (two clades) and Owenia fusiformis (three clades) were compared using a fragment of the mitochondrial cytochrome oxidase I gene (mtCOI). All lineages were present along the biogeographic transition zone on the north coast of Brittany (France) and we found evidence pointing towards congruence in the timing of cladogenic events between Pectinaria sp. (P. auricoma/P. belgica and P. koreni) and Owenia sp., suggesting a shared history of vicariant events. More conserved 16SrRNA sequences obtained from four species of Pectinariidae together with mtCOI sequences of P. koreni seem consistent with an initial establishment of pectinariids in the north, and a southward colonization of the Northeast Atlantic. Phylogeographic patterns in O. fusiformis were also consistent with a north/south pattern of lineage splitting and congruent levels of divergence were detected between lineages of both species. We observed signatures of both persistence in small northern glacial refugia, and of northwards range expansion from regions situated closer to the Mediterranean. However, whether the recolonization of the Northeast Atlantic by both species actually reflects separate interglacial periods is unclear with regards to the lack of molecular clock calibration in coastal polychaete species.

St. Lucie Estuary and Indian River Lagoon conceptual ecological model

The St. Lucie Estuary is one of the largest brackish water bodies on the east coast of Florida, USA and a major tributary to southern Indian River Lagoon. The Indian River Lagoon is a biogeographic transition zone, rich in habitats and species, with the greatest species diversity of any estuary in North America. Habitats and species diversity in the lagoon system are believed to be affected by the decline in water and sediment quality. The health of the system is being affected by water management and land-use development in this rapidly growing area of South Florida. These affects are expressed through the six major stressors identified in this conceptual ecological model. The model diagram and its associated text describe the effects of these stressors on the key ecological attributes of the system and are a way to describe both the well-known linkages and pathways between these stressors and the detrimental impacts they have on the ecology of the system. This model also provides a means to describe some of the uncertainties and associated research that will be needed to fine tune our understanding of some of the more complicated ecological interactions and interdependencies in order to carry out effectively the goals and objectives of Everglades restoration in this system and adaptively manage the restoration into the future.

Population differentiation of the Atlantic spotted dolphin (Stenella frontalis) in the western North Atlantic, including the Gulf of Mexico

Information about the genetic population structure of the Atlantic spotted dolphin [Stenella frontalis (G. Cuvier 1829)] in the western North Atlantic would greatly improve conservation and management of this species in USA waters. To this end, mitochondrial control region sequences and five nuclear microsatellite loci were used to test for genetic differentiation of Atlantic spotted dolphins in the western North Atlantic, including the Gulf of Mexico (n=199). Skin tissue samples were collected from 1994–2000. Significant heterozygote deficiencies in three microsatellite loci within samples collected off the eastern USA coast prompted investigation of a possible Wahlund effect, resulting in evidence for previously unsuspected population subdivision in this region. In subsequent analyses including three putative populations, two in the western North Atlantic (n=38, n=85) and one in the Gulf of Mexico (n=76), significant genetic differentiation was detected for both nuclear DNA (RST=0.096, P≤0.0001) and mitochondrial DNA (ΦST=0.215, P≤0.0001), as well as for all pair-wise population comparisons for both markers. This genetic evidence for population differentiation coupled to known biogeographic transition zones at Cape Hatteras, North Carolina and Cape Canaveral, Florida, USA, evidence of female philopatry, and preliminary support for significant genetic differences between previously documented morphotypes of Atlantic spotted dolphins in coastal and offshore waters all indicate that the biology and life history of this species is more complex than previously assumed. Assumptions of large, panmictic populations might not be accurate in other areas where S. frontalis is continuously distributed (e.g., eastern Atlantic), and could have a detrimental effect on long-term viability and maintenance of genetic diversity in this species in regions where incidental human-induced mortality occurs.

Incipient speciation ofCatostylus mosaicus(Scyphozoa, Rhizostomeae, Catostylidae), comparative phylogeography and biogeography in south‐east Australia

AbstractAim Phylogeography provides a framework to explain and integrate patterns of marine biodiversity at infra‐ and supra‐specific levels. As originally expounded, the phylogeographic hypotheses are generalities that have limited discriminatory power; the goal of this study is to generate and test specific instances of the hypotheses, thereby better elucidating both local patterns of evolution and the conditions under which the generalities do or do not apply.Location Coastal south‐east Australia (New South Wales, Tasmania and Victoria), and south‐west North America (California and Baja California).Methods Phylogeographic hypotheses specific to coastal south‐east Australia were generateda priori, principally from existing detailed distributional analyses of echinoderms and decapods. The hypotheses are tested using mitochondrial cytochrome c oxidase subunit I (COI) and nuclear internal transcribed spacer 1 (ITS1) DNA sequence data describing population variation in the jellyfishCatostylus mosaicus,integrated with comparable data from the literature.Results Mitochondrial COI distinguished two reciprocally monophyletic clades ofC. mosaicus(mean ± SD: 3.61 ± 0.40% pairwise sequence divergence) that were also differentiated by ITS1 haplotype frequency differences; the boundary between the clades was geographically proximate to a provincial zoogeographic boundary in the vicinity of Bass Strait. There was also limited evidence of another genetic inhomogeneity, of considerably smaller magnitude, in close proximity to a second hypothesized zoogeographic discontinuity near Sydney. Other coastal marine species also show genetic divergences in the vicinity of Bass Strait, although they are not closely concordant with each other or with reported biogeographic discontinuities in the region, being up to several hundreds of kilometres apart. None of the species studied to date show a strong phylogeographic discontinuity across the biogeographic transition zone near Sydney.Main conclusions Patterns of evolution in the Bass Strait and coastal New South Wales regions differ fundamentally because of long‐term differences in extrinsic factors. Since the late Pliocene, periods of cold climate and low sea‐level segregated warm temperate organisms east or west of an emergent Bassian Isthmus resulting in population divergence and speciation; during subsequent periods of warmer and higher seas, sister taxa expanded into the Bass Strait region leading to weakly correlated phylogeographic and biogeographic patterns. The Sydney region, by contrast, has been more consistently favourable to shifts in species’ ranges and long‐distance movement, resulting in a lack of intra‐specific and species‐level diversification. Comparisons between the Sydney and Bass Strait regions and prior studies in North America suggest that vicariance plays a key role in generating coastal biodiversity and that dispersal explains many of the deviations from the phylogeographic hypotheses.

Phylogeographic evidence for the existence of an ancient biogeographic barrier: the Isthmus of Kra Seaway

Biogeographic boundaries are characterised by distinct faunal and floral assemblages restricted on either side, but patterns among groups of taxa often vary and may not be discrete. Historical biogeography as a consequence, while providing crucial insights into the relationship between biological diversity and earth history, has some limitations. Patterns of intraspecific molecular variation, however, may show unambiguous evidence for such historical divides, and can be used to test competing biogeographic hypotheses (often based on the dispersal-vicariance debate). Here, we utilise this method to test the hypothesis that a major biogeographic transition zone between the Sundaic and Indochinese biotas, located just north of the Isthmus of Kra in SE Asia, is the result of Neogene marine transgressions that breached the Isthmus in two locations for prolonged periods of time (>1 million year duration). Phylogeographic analyses of a freshwater decapod crustacean, the giant freshwater prawn Macrobrachium rosenbergii, strongly supports the historical existence of the more northerly postulated seaway. Results presented here highlight the power of utilising intraspecific molecular variation in testing biogeographical hypotheses.

Morphology and reproduction of Predaea feldmannii Børgesen (Nemastomataceae, Rhodophyta), an uncommon species from Brazil

The coast of Espirito Santo State is located in a biogeographic transition zone presenting high diversity. A renewed interest in this region occurred in the 1990s, resulting in various new records and new species descriptions added to the Brazilian marine flora. The study of the infralitoral of this region is just beginning, and a detailed exploration with use of Scuba diving is revealing a flora containing many little-known taxa, particularly of red algae. As a first result, Predaea feldmannii Borgesen is being described for the Brazilian coast. The occurrence of the genus Predaea in Brazil has been considered with restriction since representatives of this genus had been referred only once by Howe & Taylor in 1931, being first considered as Platoma. The occurrence of Predaea in Brazil is now confirmed, and its vegetative and reproductive structures are described in detail. Predaea feldmannii can be recognized by having gonimoblast initial formed on a bulge of the connecting filament, cortical filaments of nearly equal lengths, lack of gland cells, dense clusters of nutritive cells borne only on cells immediatelly contiguous to the auxiliary cell, and a three-celled carpogonial branch.

Plant diversity, biogeography and environment in Iberia: Patterns and possible causal factors

Abstract. We associated patterns of plant diversity with possible causal factors by considering 93 local regions in the Iberian Peninsula and Balearic Islands with respect to biogeography, environmental favourability, and environmental heterogeneity, and their relationship with measured species diversity at four different scales: mean local species richness standardized at a grain of 100 m2, total species richness in a community type within a region (regional community richness), mean compositional similarity, and mosaic diversity.Local regions in biogeographic transition zones to the North African and Atlantic floras had higher regional community richness and greater mosaic diversity than did non‐transitional regions, whereas no differences existed in mean local species richness or mean compositional similarity. Mean local species richness was positively related to environmental favourability as measured by actual evapotranspiration, but negatively related to total precipitation and temporal heterogeneity in precipitation. Mean local species richness was greatest in annual grassland and dwarf shrubland communities, and on calcareous bedrock types. Regional community richness was similarly related to actual evapotranspiration and total precipitation, but in addition was positively related to spatial heterogeneity in topography and soil water holding capacity. Mean compositional similarity decreased with increasing spatial heterogeneity and temperature seasonality. Mosaic diversity, a measure of complexity, increased with increasing local and regional richness.We hypothesize that these relationships can be explained by four ecological and evolutionary classes of causal factors: numbers of individuals, intermediate environments, limits to adaptation, and niche variation. These factors operate at various scales and manifest themselves in various ways. For example, at the site level, apparently processes that increase the number of individuals increase mean local species richness, but at the level of the entire region no such effects were found.