Comparative phylogeography of African savannah ungulates

The savannah biome of sub-Saharan Africa harbours the highest diversity of ungulates (hoofed mammals) on Earth. In this review, we compile population genetic data from 19 codistributed ungulate taxa of the savannah biome and find striking concordance in the phylogeographic structuring of species. Data from across taxa reveal distinct regional lineages, which reflect the survival and divergence of populations in isolated savannah refugia during the climatic oscillations of the Pleistocene. Data from taxa across trophic levels suggest distinct savannah refugia were present in West, East, Southern and South-West Africa. Furthermore, differing Pleistocene evolutionary biogeographic scenarios are proposed for East and Southern Africa, supported by palaeoclimatic data and the fossil record. Environmental instability in East Africa facilitated several spatial and temporal refugia and is reflected in the high inter- and intraspecific diversity of the region. In contrast, phylogeographic data suggest a stable, long-standing savannah refuge in the south.     

Bridging the gap: western rock skinks (Trachylepis sulcata) have a short history in South Africa

Phylogeographic patterns in wide-ranging species in southern Africa remain largely unexplored, especially in areas north of South Africa. Here, we investigate population structuring, demographic history, and the colonization pattern of the western rock skink (Trachylepis sulcata), a rock-dwelling species with a range extending from southwestern South Africa into Angola. Using 1056 bp from the mitochondrial marker ND2 and > 2.5 kb from three nuclear genes (EXPH5, KIF24, RAG-1), we constructed allele networks, generated extended Bayesian skyline plots and performed population clustering analyses. Analyses of historical demographic patterns show an overall southward range expansion from Northern Namibia into Southern Namibia and South Africa, although we find contrasting genetic breaks across these geographic regions using nuclear and mitochondrial data. We suggest that mtDNA has introgressed across a nuclear break corresponding to the Knersvlakte region of South Africa, a previously proposed biogeographic barrier for rupicolous species. This pattern of mitochondrial variation contrasts sharply to that of other South African taxa previously investigated, which all show significant mtDNA differentiation across the Knersvlakte region. Additionally, while other taxa show divergences dating to the Pliocene, T. sulcata appears to be a recent arrival in southern Africa, having crossed this barrier and colonized South Africa in the mid-Pleistocene. The complex phylogeographic history of T. sulcata corroborates the intricate patterns of genetic variation found in South African taxa and provides novel insight into historical processes affecting species distributed across Namibia.     

Idiosyncratic responses to climate‐driven forest fragmentation and marine incursions in reed frogs from Central Africa and the Gulf of Guinea Islands

Organismal traits interact with environmental variation to mediate how species respond to shared landscapes. Thus, differences in traits related to dispersal ability or physiological tolerance may result in phylogeographic discordance among co‐distributed taxa, even when they are responding to common barriers. We quantified climatic suitability and stability, and phylogeographic divergence within three reed frog species complexes across the Guineo‐Congolian forests and Gulf of Guinea archipelago of Central Africa to investigate how they responded to a shared climatic and geological history. Our species‐specific estimates of climatic suitability through time are consistent with temporal and spatial heterogeneity in diversification among the species complexes, indicating that differences in ecological breadth may partly explain these idiosyncratic patterns. Likewise, we demonstrated that fluctuating sea levels periodically exposed a land bridge connecting Bioko Island with the mainland Guineo‐Congolian forest and that habitats across the exposed land bridge likely enabled dispersal in some species, but not in others. We did not find evidence that rivers are biogeographic barriers across any of the species complexes. Despite marked differences in the geographic extent of stable climates and temporal estimates of divergence among the species complexes, we recovered a shared pattern of intermittent climatic suitability with recent population connectivity and demographic expansion across the Congo Basin. This pattern supports the hypothesis that genetic exchange across the Congo Basin during humid periods, followed by vicariance during arid periods, has shaped regional diversity. Finally, we identified many distinct lineages among our focal taxa, some of which may reflect incipient or unrecognized species.     

The evolutionary history of brown trout (Salmo trutta L.) inferred from phylogeographic, nested clade, and mismatch analyses of mitochondrial DNA variation

Phylogeographic, nested clade, and mismatch analyses of mitochondrial DNA (mtDNA) variation were used to infer the temporal dynamics of distributional and demographic history of brown trout (Salmo trutta). Both new and previously published data were analyzed for 1,794 trout from 174 populations. This combined analysis improved our knowledge of the complex evolutionary history of brown trout throughout its native Eurasian and North African range of distribution in many ways. It confirmed the existence of five major evolutionary lineages that evolved in geographic isolation during the Pleistocene and have remained largely allopatric since then. These should be recognized as the basic evolutionarily significant units within brown trout. Finer phylogeographic structuring was also resolved within major lineages. Contrasting temporal juxtaposition of different evolutionary factors and timing of major demographic expansions were observed among lineages. These unique evolutionary histories have been shaped both by the differential latitudinal impact of glaciations on habitat loss and potential for dispersal, as well as climatic impacts and landscape heterogeneity that translated in a longitudinal pattern of genetic diversity and population structuring at more southern latitudes. This study also provided evidence for the role of biological factors in addition to that of physical isolation in limiting introgressive hybridization among major trout lineages.     

Strict consistency between genetic and topographic landscapes of the brown tree frog (Buergeria robusta) in Taiwan

Taiwan presents an excellent opportunity to build a phylogeographic paradigm for fine-scaled differentiation occurring within short distances on an single island. Due to the limitation of habitat availability on the island, demographic histories of species in Taiwan were strongly influenced by glacial-interglacial cycles. Nevertheless, there are relatively few studies demonstrating such phylogeographic patterns for islands, especially in subtropical Asia. In this study, we aim to construct the genetic landscape of a philopatric stream frog Buergeria robusta by an intense and fine-scaled collection throughout the island. The deduced genetic landscape of B. robusta presented extremely high congruence with the actual topography of Taiwan. Two major lineages were found on the eastern and the western sides of Taiwan with a non-overlapping distribution, indicating the importance of the Central Mountain Range as the major biogeographic barrier. Both clades showed a strong and congruent tendency of demographic or distributional expansion in recent history based on different analyses. Population expansion of such a subtropical lowland species might be a result from a release of available habitat in post-glacial periods.     

Phylogeographic concordance factors quantify phylogeographic congruence among co‐distributed species in the Sarracenia alata pitcher plant system

Comparative phylogeographic investigations have identified congruent phylogeographic breaks in co‐distributed species in nearly every region of the world. The qualitative assessments of phylogeographic patterns traditionally used to identify such breaks, however, are limited because they rely on identifying monophyletic groups across species and do not account for coalescent stochasticity. Only long‐standing phylogeographic breaks are likely to be obvious; many species could have had a concerted response to more recent landscape events, yet possess subtle signs of phylogeographic congruence because ancestral polymorphism has not completely sorted. Here, we introduce Phylogeographic Concordance Factors (PCFs), a novel method for quantifying phylogeographic congruence across species. We apply this method to the Sarracenia alata pitcher plant system, a carnivorous plant with a diverse array of commensal organisms. We explore whether a group of ecologically associated arthropods have co‐diversified with the host pitcher plant, and identify if there is a positive correlation between ecological interaction and PCFs. Results demonstrate that multiple arthropods share congruent phylogeographic breaks with S. alata, and provide evidence that the level of ecological association can be used to predict the degree of similarity in the phylogeographic pattern. This study outlines an approach for quantifying phylogeographic congruence, a central concept in biogeographic research.     

Genetic consequences of population expansions and contractions in the common hippopotamus (Hippopotamus amphibius) since the Late Pleistocene

Over the past two decades, an increasing amount of phylogeographic work has substantially improved our understanding of African biogeography, in particular the role played by Pleistocene pluvial–drought cycles on terrestrial vertebrates. However, still little is known on the evolutionary history of semi‐aquatic animals, which faced tremendous challenges imposed by unpredictable availability of water resources. In this study, we investigate the Late Pleistocene history of the common hippopotamus (Hippopotamus amphibius), using mitochondrial and nuclear DNA sequence variation and range‐wide sampling. We documented a global demographic and spatial expansion approximately 0.1–0.3 Myr ago, most likely associated with an episode of massive drainage overflow. These events presumably enabled a historical continent‐wide gene flow among hippopotamus populations, and hence, no clear continental‐scale genetic structuring remains. Nevertheless, present‐day hippopotamus populations are genetically disconnected, probably as a result of the mid‐Holocene aridification and contemporary anthropogenic pressures. This unique pattern contrasts with the biogeographic paradigms established for savannah‐adapted ungulate mammals and should be further investigated in other water‐associated taxa. Our study has important consequences for the conservation of the hippo, an emblematic but threatened species that requires specific protection to curtail its long‐term decline.     

Effects of vicariant barriers, habitat stability, population isolation and environmental features on species divergence in the south-western Australian coastal reptile community

Identifying explicit hypotheses regarding the factors determining genetic structuring within species can be difficult, especially in species distributed in historically dynamic regions. To contend with these challenges, we use a framework that combines species distribution models, environmental data and multi-locus genetic data to generate and explore phylogeographic hypotheses for reptile species occupying the coastal sand-dune and sand-plain habitats of the south-western Australian biodiversity hotspot, a community which has both a high diversity of endemics and has varied dramatically in spatial extent over time. We use hierarchical amova, summary statistic and distance-based analyses to explicitly test specific phylogeographic hypotheses. Namely, we test if biogeographic vicariance across barriers, habitat stability, population isolation along a linear habitat or fragmentation across different environments can explain genetic divergence within five co-distributed squamate reptile species. Our results show that patterns of genetic variation reflect complex and species-specific interactions related to the spatial distribution of habitats present currently and during repeated glacial minima, as opposed to being associated with historical factors such as habitat stability between glacial and inter-glacial periods or vicariant barriers. We suggest that the large impact of habitat characteristics over time (i.e. relative levels of habitat connectivity, climatic gradients and spatial heterogeneity of soil types) reflects the ecological restrictions of the sand-dune and sand-plain reptile communities and may explain the lack of concordance across taxa. The study demonstrates the general utility of the approach for assemblage-level, as well as single species, phylogeographic study, including its usefulness for exploring biologically informed hypotheses about what factors have influenced patterns of genetic variation.     

Phylogeography and biogeography of the lower Central American Neotropics: diversification between two continents and between two seas

Lower Central America (LCA) provides a geologically complex and dynamic, richly biodiverse model for studying the recent assembly and diversification of a Neotropical biota. Here, we review the growing literature of LCA phylogeography studies and their contribution to understanding the origins, assembly, and diversification of the LCA biota against the backdrop of regional geologic and climatic history, and previous biogeographical inquiry. Studies to date reveal that phylogeographical signal within taxa of differing distributions reflects a diversity of patterns and processes rivalling the complexities of LCA landscapes themselves. Even so, phylogeography is providing novel insights into regional diversification (e.g. cryptic lineage divergences), and general evolutionary patterns are emerging. Congruent multi‐taxon phylogeographic breaks are found across the Nicaraguan depression, Chorotega volcanic front, western and central Panama, and the Darién isthmus, indicating that a potentially shared history of responses to regional‐scale (e.g. geological) processes has shaped the genetic diversity of LCA communities. By contrast, other species show unique demographic histories in response to overriding historical events, including no phylogeographic structure at all. These low‐structure or incongruent patterns provide some evidence for a role of local, ecological factors (e.g. long‐distance dispersal and gene flow in plants and bats) in shaping LCA communities. Temporally, comparative phylogeographical structuring reflects Pliocene–Pleistocene dispersal and vicariance events consistent with the timeline of emergence of the LCA isthmus and its major physiographic features, e.g. cordilleras. We emphasise the need to improve biogeographic inferences in LCA through in‐depth comparative phylogeography projects capitalising on the latest statistical phylogeographical methods. While meeting the challenges of reconstructing the biogeographical history of this complex region, phylogeographers should also take up the critical service to society of applying their work to the conservation of its fascinating biodiversity.     

Comparative phylogeography of two open forest frogs from eastern Australia

We investigated the phylogeography of two closely related Australian frog species from open forest habitats, Limnodynastes tasmaniensis and L. peronii , using mitochondrial ND4 sequence data. Comparison of our results with previous work on Litoria fallax allowed us to test the generality of phylogeographic patterns among non-rainforest anurans along the east coast of Australia. In general, there was no strong evidence for congruence between overall patterns of genetic structure in the three species. However, phylogenetic breaks congruent with the position of the Burdekin Gap were detected at some level in all species. As previously noted for closed forest taxa, this area of dry habitat appears to have been an important influence on the evolution of several open forest taxa. There were broad geographic similarities in the phylogenetic structuring of southern populations of L. peronii and L. tasmaniensis. Contrarily, although the McPherson Range has previously been noted to coincide geographically with a major mtDNA phylogenetic break in Litoria fallax this pattern is not apparent in L. peronii or L. tasmaniensis. It appears that major phylogeographic splits within L. peronii and L. tasmaniensis may predate the Quaternary. We conclude that phylogeographies of open forest frogs are complex and more difficult to predict than for rainforest taxa, mainly due to an absence of palæomodels for historical distributions of non-rainforest habitats.     

Speciation durations and Pleistocene effects on vertebrate phylogeography.

An approach applied previously to avian biotas is extended in this paper to other vertebrate classes to evaluate Pleistocene phylogeographic effects and to estimate temporal spans of the speciation process (speciation durations) from mitochondrial (mt) DNA data on extant taxa. Provisional molecular clocks are used to date population separations and to bracket estimates of speciation durations between minimum and maximum values inferred from genetic distances between, respectively, extant pairs of intraspecific phylogroups and sister species. Comparisons of genetic-distance trends across the vertebrate classes reveal the following: (i) speciation durations normally entail at least two million years on average; (ii) for mammals and birds, Pleistocene conditions played an important role in initiating phylogeographic differentiation among now-extant conspecific populations as well as in further sculpting pre-existing phylogeographic variety into many of today''s sister species; and (iii) for herpetofauna and fishes, inferred Pleistocene biogeographic influences on present-day taxa differ depending on alternative but currently plausible mtDNA rate calibrations.     

Lineage-specific late pleistocene expansion of an endemic subtropical gossamer-wing damselfly, Euphaea formosa, in Taiwan

Background  

Pleistocene glacial oscillations have significantly affected the historical population dynamics of temperate taxa. However, the general effects of recent climatic changes on the evolutionary history and genetic structure of extant subtropical species remain poorly understood. In the present study, phylogeographic and historical demographic analyses based on mitochondrial and nuclear DNA sequences were used. The aim was to investigate whether Pleistocene climatic cycles, paleo-drainages or mountain vicariance of Taiwan shaped the evolutionary diversification of a subtropical gossamer-wing damselfly, Euphaea formosa.     

Pleistocene climatic changes drive diversification across a tropical savanna

Spatial responses of species to past climate change depend on both intrinsic traits (climatic niche breadth, dispersal rates) and the scale of climatic fluctuations across the landscape. New capabilities in generating and analysing population genomic data, along with spatial modelling, have unleashed our capacity to infer how past climate changes have shaped populations, and by extension, complex communities. Combining these approaches, we uncover lineage diversity across four codistributed lizards from the Australian Monsoonal Tropics and explore how varying climatic tolerances interact with regional climate history to generate common vs. disparate responses to late Pleistocene change. We find more divergent spatial structuring and temporal demographic responses in the drier Kimberley region compared to the more mesic and consistently suitable Top End. We hypothesize that, in general, the effects of species’ traits on sensitivity to climate fluctuation will be more evident in climatically marginal regions. If true, this points to the need in climatically marginal areas to craft more species‐(or trait)‐specific strategies for persistence under future climate change.     

Influence of drainage divides versus arid corridors on genetic structure and demography of a widespread freshwater turtle,Emydura macquarii krefftii,from Australia

The influence of Pleistocene climatic cycles on Southern Hemisphere biotas is not yet well understood. Australia's eastern coastal margin provides an ideal setting for examining the relative influence of landscape development, sea level fluctuation, and cyclic climatic aridity on the evolution of freshwater biodiversity. We examined the impact of climatic oscillations and physical biogeographic barriers on the evolutionary history of the wide‐ranging Krefft's river turtle (Emydura macquarii krefftii), using range‐wide sampling (649 individuals representing 18 locations across 11 drainages) and analysis of mitochondrial sequences (~1.3‐kb control region and ND4) and nuclear microsatellites (12 polymorphic loci). A range of phylogeographic (haplotype networks, molecular dating), demographic (neutrality tests, mismatch distributions), and population genetic analyses (pairwise F_ST, analysis of molecular variance, Bayesian clustering analysis) were implemented to differentiate between competing demographic (local persistence vs. range expansion) and biogeographic (arid corridor vs. drainage divide) scenarios. Genetic data reveal population genetic structure in Krefft's river turtles primarily reflects isolation across drainage divides. Striking north‐south regional divergence (2.2% ND4 p‐distance; c. 4.73 Ma, 95% higher posterior density (HPD) 2.08–8.16 Ma) was consistent with long‐term isolation across a major drainage divide, not an adjacent arid corridor. Ancient divergence among regional lineages implies persistence of northern Krefft's populations despite the recurrent phases of severe local aridity, but with very low contemporary genetic diversity. Stable demography and high levels of genetic diversity are inferred for southern populations, where aridity was less extreme. Range‐wide genetic structure in Krefft's river turtles reflects contemporary and historical drainage architecture, although regional differences in the extent of Plio–Pleistocene climatic aridity may be reflected in current levels of genetic diversity.     

Landscape genetics in a changing world: disentangling historical and contemporary influences and inferring change

Landscape genetics seeks to determine the effect of landscape features on gene flow and genetic structure. Often, such analyses are intended to inform conservation and management. However, depending on the many factors that influence the time to reach equilibrium, genetic structure may more strongly represent past rather than contemporary landscapes. This well‐known lag between current demographic processes and population genetic structure often makes it challenging to interpret how contemporary landscapes and anthropogenic activity shape gene flow. Here, we review the theoretical framework for factors that influence time lags, summarize approaches to address this temporal disconnect in landscape genetic studies, and evaluate ways to make inferences about landscape change and its effects on species using genetic data alone or in combination with other data. Those approaches include comparing correlation of genetic structure with historical versus contemporary landscapes, using molecular markers with different rates of evolution, contrasting metrics of genetic structure and gene flow that reflect population genetic processes operating at different temporal scales, comparing historical and contemporary samples, combining genetic data with contemporary estimates of species distribution or movement, and controlling for phylogeographic history. We recommend using simulated data sets to explore time lags in genetic structure, and argue that time lags should be explicitly considered both when designing and interpreting landscape genetic studies. We conclude that the time lag problem can be exploited to strengthen inferences about recent landscape changes and to establish conservation baselines, particularly when genetic data are combined with other data.     

LIFE-HISTORY VARIATION AND COMPARATIVE PHYLOGEOGRAPHY OF DARTERS (PISCES: PERCIDAE) FROM THE NORTH AMERICAN CENTRAL HIGHLANDS

Phylogeography seeks to evaluate the relationship between genetic variation and geographic distribution of a species to examine the influence of historical events on divergence. Congruent phylogeographic patterns in codistributed species indicate historical association of the taxa being compared, and the uniform action of biogeographic events in shaping genetic variation. We sought to evaluate the congruence of patterns of genetic variation of five closely related fish species across a well-defined biogeographic boundary. We gathered allozymic and mitochondrial DNA (mtDNA) sequence data for five species of darters (Percidae: Etheostomatini) from populations distributed among biogeographic regions in the Ozark and Ouachita highlands of the south-central United States. Comparisons among species revealed noncongruence in the magnitude of genetic divergence in both allozymes and mtDNA sequences. We hypothesized that noncongruence resulted, in part, from differences in life histories of the species in our comparison. To address this hypothesis, we evaluated the association between gene flow (measured by N_em) and variation in body size and fecundity variables because they have been shown to influence gene flow in fishes. Correlation analysis revealed an association between gene flow and fecundity (r = 0.88), but not with body size (r = 0.36) or reproductive investment per individual (r = –0.23). The result was similar when independent contrasts of the original variables were used in correlation analyses. Phylogeographic analysis of mtDNA sequence data indicated the importance of history, evident in gene trees of Percina nasuta and Percina phoxocephala. Divergence rates between these two taxa may differ because of historically persistent differences in population sizes, reflected in present-day abundance and fecundity differences. Conversely, Percina caprodes showed little evidence of divergence in mtDNA sequences and yielded the highest mean N_em values from allozyme data. Comparisons among closely related, codistributed taxa may help discriminate among the possibilities for noncongruence in biogeographic studies by allowing evaluation of the influence of life history on patterns of gene flow.     

INTEGRATIVE TESTING OF HOW ENVIRONMENTS FROM THE PAST TO THE PRESENT SHAPE GENETIC STRUCTURE ACROSS LANDSCAPES

Tests of the genetic structure of empirical populations typically focus on the correlative relationships between population connectivity and geographic and/or environmental factors in landscape genetics. However, such tests may overlook or misidentify the impact of candidate factors on genetic structure, especially when connectivity patterns differ between past and present populations because of shifting environmental conditions over time. Here we account for the underlying demographic component of population connectivity associated with a temporarily dynamic landscape in tests of the factors structuring population genetic variation in an Australian lizard, Lerista lineopunctulata, from 24 nuclear loci. Correlative tests did not support significant effect from factors associated with a static contemporary landscape. However, spatially explicit demographic modeling of genetic differentiation shows that changes in environmental conditions (as estimated from paleoclimatic data) and corresponding distributional shifts from the past to present landscape significantly structures genetic variation. Results from model‐based inference (i.e., from an integrative modeling approach that generates spatially explicit expectations that are tested with approximate Bayesian computation) contrasts with those from correlative analyses, highlighting the importance of expanding the landscape genetic perspective to tests the links between pattern and process, revealing how factors shape patterns of genetic variation within species.     

Patterns of genetic diversity in the critically endangered Central American river turtle: human influence since the Mayan age?

We conducted a phylogeographic analysis of the strictly aquatic and critically endangered Central American river turtle, Dermatemys mawii, as part of a conservation management program for the species. We sampled 238 individuals from 15 different localities throughout the species range. Using sequence fragments from the mtDNA Cyt b and ND4 genes, we identified 16 different haplotypes. Overall, our results reveal a signal of phylogeographic structure throughout the range, which appears to have been secondarily blurred by extensive gene flow. Notably, this also applies to genetic structuring across three major hydrological basins that pose biogeographic breaks in other aquatic taxa. Divergence times of mtDNA haplotypes in D. mawii suggest that the main lineages split in the Pliocene–Pleistocene (3.73–0.227 MA) and demographic tests indicate that the species has undergone drastic demographic size fluctuations since this time period. One ancient haplotype (1D) was found to exhibit sequence divergence of up to 2% from other haplogroups. Divergence of this magnitude is indicative of species level differentiation in other turtle genera. Haplotype 1D was found in only two localities, Sarstun and Salinas, but specimens with other haplotypes were also found in those localities. It is not known whether the individuals with the 1D haplotype interbreed with non-1D individuals. Our results suggest that human activity, such as harvesting and long distance transport of animals, may have influenced the current patterns of genetic diversity. For more than 2000 years, D. mawii has been consumed by people from Middle American cultures, and the archeological record contains strong evidence that the Mayans transported animals between villages and far away from their natural distribution range. Therefore, the large-scale pattern of haplotype sharing even across hydrological barriers, the observed low haplotype diversity in some populations and the contemporary absence of a pronounced phylogeographic pattern is likely due to a combination of population expansions, gene flow, extensive human-mediated-movements and recent bottlenecks resulting from over-harvesting.     

Phylogeographic concordance in the southeastern United States: the flatwoods salamander, Ambystoma cingulatum, as a test case

Well-supported, congruent phylogeographic and biogeographic patterns permit the development of a priori phylogeographic and distributional predictions. In the southeastern Coastal Plain of the United States, the common discovery of east-west disjunctions (phylogeographic breaks and species' distributional boundaries) suggests that similar disjunctions should occur in codistributed taxa. Despite the near ubiquity of these disjunctions, the most recent morphological analyses of the flatwoods salamander, Ambystoma cingulatum, indicate that none occur in this low-vagility, Coastal Plain endemic. We conducted molecular and morphological analyses to test whether the flatwoods salamander is an exception to this common biogeographic pattern. Assessing geographic variation in this species is also an important management tool for this threatened, declining amphibian. We demonstrate that flatwoods salamanders, as predicted by comparisons to codistributed taxa, are polytypic with a major disjunction at the Apalachicola River. This drainage is a common site for east-west phylogeographic breaks, probably because repeated marine embayments during the Pliocene and Pleistocene interglacials generated barriers to gene flow. Based on mitochondrial DNA, morphology, and allozymes, we recognize two species of flatwoods salamanders -- Ambystoma cingulatum to the east of the Apalachicola drainage and Ambystoma bishopi to the west. Given this increased diversity, the conservation status of these two taxa may warrant re-evaluation. More generally, these results emphasize that in the absence of taxon-specific data, established comparative patterns can provide strong expectations for designing management units for unstudied species of conservation concern.     

Large‐scale distribution patterns of mangrove nematodes: A global meta‐analysis

Mangroves harbor diverse invertebrate communities, suggesting that macroecological distribution patterns of habitat‐forming foundation species drive the associated faunal distribution. Whether these are driven by mangrove biogeography is still ambiguous. For small‐bodied taxa, local factors and landscape metrics might be as important as macroecology. We performed a meta‐analysis to address the following questions: (1) can richness of mangrove trees explain macroecological patterns of nematode richness? and (2) do local landscape attributes have equal or higher importance than biogeography in structuring nematode richness? Mangrove areas of Caribbean‐Southwest Atlantic, Western Indian, Central Indo‐Pacific, and Southwest Pacific biogeographic regions. We used random‐effects meta‐analyses based on natural logarithm of the response ratio (lnRR) to assess the importance of macroecology (i.e., biogeographic regions, latitude, longitude), local factors (i.e., aboveground mangrove biomass and tree richness), and landscape metrics (forest area and shape) in structuring nematode richness from 34 mangroves sites around the world. Latitude, mangrove forest area, and forest shape index explained 19% of the heterogeneity across studies. Richness was higher at low latitudes, closer to the equator. At local scales, richness increased slightly with landscape complexity and decreased with forest shape index. Our results contrast with biogeographic diversity patterns of mangrove‐associated taxa. Global‐scale nematode diversity may have evolved independently of mangrove tree richness, and diversity of small‐bodied metazoans is probably more closely driven by latitude and associated climates, rather than local, landscape, or global biogeographic patterns.