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opencc-zeroNov 2020View details →

Data from: Modelling species distributions limited by geographic barriers: a case study with African and American primates

Aim: The boundaries of species distributions are often shaped by natural barriers such as mountains and rivers, but species distribution models usually fail to include these constraints. We tested several approaches that include barriers as explanatory variables in species distribution models. Location: Africa and South America. Time period: Current Major taxa studied: Primates Methods: We modelled the ranges of pairs of species separated by a river taking into account three explanatory components: the environment (ecosystems, topo-hydrography, climate, human pressure), the spatial structure shaped by history and population dynamics (using a trend-surface approach), and rivers as naturals barriers to dispersal (using a binary cis-trans variable that describes both sides of the river). To assess how the addition of a spatial structure and the barrier could improve distribution models, we used a nested approach by comparing models based on: a) the environment; b) the environment and the spatial structure; and c) the environment, the spatial structure and the river. These models were constructed using the favourability functions. Results: There was a decreased occurrence of high-favourability values in the opposite side of the rivers in models that included the spatial structure of distributions, compared to models based on environment alone. This decrease was more marked when the description of the spatial structure was made more flexible. However, model performance was significantly improved by the inclusion of cis-trans variables that identified areas on the opposite side as totally unfavourable. Main conclusions: The performance of distribution models can improve by the use of approaches that describe barriers. Although adding the location of geographic units in relation to a river appears to be the most accurate way to define the presence of a barrier, defining this variable may be challenging. A suitable alternative is to analyse the spatial structure of distributions using a flexible approach.

FIGURE 4 in Phenotypic divergence in large sized cricket frog species that crossed the geographical barriers within peninsular India

FIGURE 4. Principal Component Analysis for male individuals of F. kalinga (from WG and EG), F. goemchi and F. kudremukhensis using six morphometric characters (Table 2) transformed to their ratio to SVL for from the Western Ghats.

FIGURE 3. Principal Component Analysis for male individuals using 31 in Phenotypic divergence in large sized cricket frog species that crossed the geographical barriers within peninsular India

FIGURE 3. Principal Component Analysis for male individuals using 31 morphometric characters (Table 1) transformed to their ratio to SVL for F. kalinga from the Eastern Ghats and the Western Ghats.

FIGURE 2 in Phenotypic divergence in large sized cricket frog species that crossed the geographical barriers within peninsular India

FIGURE 2. Maximum Likelihood phylogeny for the large sized fejervaryan frogs having predominant distribution in the Western Ghats / Eastern Ghats' (Figure 2, Phuge et al. 2019) with the present data based on 529 bp of mitochondrial 16S rRNA gene.

FIGURE 1 in Phenotypic divergence in large sized cricket frog species that crossed the geographical barriers within peninsular India

FIGURE 1. Details of the type localities for the species of Fejervarya described from peninsular India (1. F. orissaensis; 2. F. kalinga (from the Eastern Ghats, marked by a star); 3. F. marathi; 4. F. syhadrensis; 5. F. cepfi; 6. F. goemchi; 7. F. gomantaki; 8. New collections of F. kalinga from the Western Ghats (marked by a star); 9. F. krishnan; 10. F. modesta; 11. F. mysorensis;12. F. kudremukhensis; 13. F. sahyadris; 14. F. rufescens; 15.F. sauriceps;16. F. caperata; 17. F. mudduraja; 18. F. murthii; 19. F. nilagirica; 20. F. neilcoxi; 21. F. kadar; 22. F. parambikulamana; 23. F. keralensis; 24. F. manoharani and 25. F. agricola;)

FIGURE 5 in Phenotypic divergence in large sized cricket frog species that crossed the geographical barriers within peninsular India

FIGURE 5. Fejervarya kalinga in life from A) the Western Ghats (Sirsi, Uttara Kannada, Karnataka); B) the Eastern Ghats (Sileru, Vishakapatanam, Andhra Pradesh).

opencc-zeroDec 2016View details →

Data from: Dispersal barriers and climate determine the geographic distribution of the helicopter damselfly Mecistogaster modesta

Species' ranges are typically constrained by the interplay of physical barriers to dispersal, environmental requirements such as suitable climatic conditions and biotic constraints such as from predation or competition. However, teasing apart the relative importance of these constraints in determining species distributions still represents a major challenge for ecologists. The Neotropical damselfly Mecistogaster modesta (Coenagrionidae: Odonata) inhabits wet and moist forests in mainland Central America and north-western South America. This habitat specialist spends its larval development exclusively in tank bromeliads, where it acts as a keystone predator within the aquatic food web. Although tank-forming bromeliads occur from the southern United States throughout most of South America, M. modesta is absent from the Caribbean islands and South America south-east of the Andes mountain chain. We employed species distribution models to explore the relative importance of physical barriers (Andes mountain range and oceanic barriers), climate (mean annual temperature and annual precipitation) and biotic interactions (competition from other bromeliad-dwelling odonates) in limiting the geographic distribution of M. modesta. We found that dispersal barriers strongly limit the geographic distribution of M. modesta. In addition, its range is restricted by low temperatures and low precipitation. Competition from other bromeliad-dwelling odonates was not important in limiting the damselfly's range. Because of the physical barriers to dispersal, M. modesta does not occupy its full potential geographic range. Specifically, our model predicted suitable habitat on the Caribbean islands and throughout most of South America, where the species is currently absent. These findings have important conservation implications, particularly as the aridification of rainforests and subsequent localised extinctions due to climate change continue. On the other hand, the species may respond to warming temperatures by tracking climate to higher elevations, with subsequent effects on naïve high-elevation bromeliad food webs. An upwards migration could also increase the probability of M. modesta overcoming the dispersal barrier presented by the Andes, enabling the damselfly to invade large areas of suitable habitat in South America.

opencc-zeroDec 2012View details →

Data from: The role of chromosomal rearrangements and geographical barriers in the divergence of lineages in a South American subterranean rodent (Rodentia: Ctenomyidae: Ctenomys minutus)

Identifying factors and the extent of their roles in the differentiation of populations is of great importance for understanding the evolutionary process in which a species is involved. Ctenomys minutus is a highly karyotype- polymorphic subterranean rodent, with diploid numbers ranging from 42 to 50 and autosomal arm numbers ranging from 68 to 80, comprising a total of 45 karyotypes described so far. This species inhabits the southern Brazilian coastal plain, which has a complex geological history, with several potential geographical barriers acting on different time scales. We assessed the geographical genetic structure of C. minutus, examining 340 individuals over the entire distributional range and using information from chromosomal rearrangements, mitochondrial DNA (mtDNA) sequences, and 14 microsatellite loci. The mtDNA results revealed 7 main haplogroups, with the most recent common ancestors dating from the Pleistocene, whereas clustering methods defined 12 populations. Some boundaries of mtDNA haplogroups and population clusters can be associated with potential geographical barriers to gene flow. The isolation by distance pattern also plays an important role in fine-scale genetic differentiation, which is strengthened by the narrowness of the coastal plain and by common features of subterranean rodents (i.e., small fragmented populations and low dispersal rates), which limit gene flow among populations. A step-by-step mechanism of chromosomal evolution can be suggested for this species, mainly associated with the metapopulation structure, genetic drift, and the geographical features of the southern Brazilian coastal plain. However, chromosomal variation plays no or very little role in the diversification of C. minutus populations.

opencc-zeroDec 2011View details →

Data from: Ring distributions leading to species formation: a global topographic analysis of geographic barriers associated with ring species

BACKGROUND: In the mid 20th Century, Ernst Mayr and Theodosius Dobzhansky championed the significance of circular overlaps or ring species as the perfect demonstration of speciation, yet in over 50 years since only a handful of such taxa are known. We developed a topographic model to evaluate whether the geographic barriers that favor processes leading to ring species are common or rare, and to predict where other candidate ring barriers might be found. RESULTS: Of the 952,147 geographic barriers identified on the planet, only about 1% are topographically similar to barriers associated with known ring taxa, with most of the likely candidates occurring in under-studied parts of the world (e.g., marine environments, tropical latitudes). Predicted barriers separate into two distinct categories: (i) single cohesive barriers (<50,000 km2), associated with taxa that differentiate at smaller spatial scales (salamander: Ensatina eschscholtzii; tree: Acacia karroo); and (ii) composite barriers – formed by groups of barriers (each 184,000 to 1.7 million km2) in close geographic proximity (totaling 1.9 to 2.3 million km2) – associated with taxa that differentiate at larger spatial scales (birds: Phylloscopus trochiloides and Larus [sp. argentatus and fuscus]). When evaluated globally, we find a large number of cohesive barriers that are topographically similar to those associated with known ring taxa. Yet, compared to cohesive barriers, an order of magnitude fewer composite barriers are similar to those that favor ring divergence in species with higher dispersal. CONCLUSIONS: While these findings confirm that the topographic conditions that favor evolutionary processes leading to ring speciation are in fact rare, they also suggest that many understudied natural systems could provide valuable demonstrations of continuous divergence towards the formation of new species. Distinct advantages of the model are that it (i) requires no a priori information on the relative importance of features that define barriers, (ii) can be replicated using any kind of continuously distributed environmental variable, and (iii) generates spatially explicit hypotheses of geographic species formation. The methods developed here – combined with study of the geographical ecology and genetics of taxa in their environments – should enable recognition of ring species phenomena throughout the world.

opencc-zeroDec 2013View details →

Data from: Geographical barriers and climate influence demographic history in narrowleaf cottonwoods

Studies of genetic variation can clarify the role of geography and spatio-temporal variation of climate in shaping demography, particularly in temperate zone tree species with large latitudinal ranges. Here, we examined genetic variation in narrowleaf cottonwood, Populus angustifolia, a dominant riparian tree. Using multi-locus surveys of polymorphism in 363 individuals across the species' 1800 km latitudinal range, we found that, first, P. angustifolia has stronger neutral genetic structure than many forest trees (simple sequence repeat (SSR) FST=0.21), with major genetic groups corresponding to large apparent geographical barriers to gene flow. Second, using SSRs and putatively neutral sequenced loci, coalescent simulations indicated that populations diverged before the last glacial maximum (LGM), suggesting the presence of population structure before the LGM. Third, the LGM and subsequent warming appear to have had different influences on each of these distinct populations, with effective population size reduction in the southern extent of the range but major expansion in the north. These results are consistent with the hypothesis that climate and geographic barriers have jointly affected the demographic history of P. angustifolia, and point the importance of both factors as being instrumental in shaping genetic variation and structure in widespread forest trees.

opencc-zeroDec 2015View details →

Data from: Geographical barriers and dispersal propensity interact to limit range expansions of Himalayan birds

Range expansions are limited by two key factors. These are (1) dispersal, which includes a species' intrinsic mobility, geographical barriers, and their interaction; and (2) the ability of a species to persist beyond its current range. I evaluate the role of these in affecting bird species distributions across the Himalayas, under a hypothesis that many species have recently expanded their range out of an eastern Pleistocene refuge. I measured wing shape as a proxy for dispersal ability and topographic complexity across the Himalayas as a proxy for dispersal barriers. As a factor affecting the potential for persistence in novel locations, I compared similarity of a species' climatic envelope in the east, the hypothesized historical refuge, and the west, the location of recent colonization. Climatic similarity, wing shape, and the interaction of topographic complexity with wing shape all contribute significantly to the range extent of a given species. The result highlights the important interaction between morphological and landscape factors in affecting successful range expansions. The two dispersal-related parameters together explain two times the variance explained by climate, but I present additional evidence that other factors besides climate—notably biotic interactions—affect the ability of a species to persist beyond its range.

opencc-zeroDec 2012View details →

Data from: Geographic population structure of the African malaria vector Anopheles gambiae suggests a role for the forest-savannah biome transition as a barrier to gene flow

The primary Afrotropical malaria mosquito vector Anopheles gambiae sensu stricto has a complex population structure. In western Africa, this species is split into two molecular forms and displays local and regional variation in chromosomal arrangements and behaviours. To investigate patterns of macro-geographic population substructure, 25 An. gambiae samples from 12 African countries were genotyped at 13 microsatellite loci. This analysis detected the presence of additional population structuring, with the M-form being subdivided into distinct west, central and southern African genetic clusters. These clusters are coincident with the central African rainforest belt and northern and southern savannah biomes, which suggests restrictions to gene flow associated with the transition between these biomes. By contrast geographically patterned population substructure appears much weaker within the S-form.

opencc-zeroDec 2015View details →

Data from: At least some meiofaunal species are not everywhere. Indication of geographic, ecological and geological barriers affecting the dispersion of species of Ototyphlonemertes (Nemertea, Hoplonemertea)

Most meiofaunal species are known to have a broad distribution with no apparent barriers to their dispersion. However, different morphological and/or molecular methods supported patterns of diversity and distribution that may be different among taxa while also conflicting within the same group. We accurately assessed the patterns of geographic distribution in actual genetic species of a marine meiofaunal animal model: Ototyphlonemertes. Specimens were collected from several sites around Europe, Northern and Central America, Southern America, Pacific Islands and Asia. We sequenced regions of two mitochondrial and two nuclear genes. Using single-gene, a concatenated data set, multilocus approaches and different DNA taxonomy methods, we disentangled the actual diversity and the spatial structures of haplotypes and tested the possible correlation between genetic diversity and geographic distance. The results show (i) the importance of using several genes to uncover both diversity and highlight phylogeographic relationships among species and that (ii) independent genetic evolutionary entities have a narrower distribution than morphological species. Moreover, (iii) a Mantel test supported a positive correlation between genetic and geographical distance. By sampling from the two sides of Isthmus of Panama, we were additionally able to identify lineage divergence times that are concordant with vicariance mechanisms caused by the geological closure of the seaway across the Isthmus. We therefore propose that in addition to distance, other geological and ecological conditions are also barriers to the dispersion of and gene flow in marine meiofaunal organisms.

Fig. 1 in Refugia and geographic barriers of populations of the desert poppy, Hunnemannia fumariifolia (Papaveraceae)

Fig. 1 Chronogram of the Papaveraceae family based on a Bayesian approach. Gray bars 95 % confidence intervals for node age estimates. Brackets identify Eucotyledoneae clade, Ranunculales clade, Proteales clade, Papaveracae family clade and the H/E Hunnemannia/

Fig. 6 a–d. Ecological niche models for H. fumariifolia populations. a in Refugia and geographic barriers of populations of the desert poppy, Hunnemannia fumariifolia (Papaveraceae)

Fig. 6 a–d. Ecological niche models for H. fumariifolia populations. a Prediction of suitable habitat in the current environment. b Prediction projected onto past climatic layers (LGM; CCSM). c Prediction under

Fig. 3 in Refugia and geographic barriers of populations of the desert poppy, Hunnemannia fumariifolia (Papaveraceae)

Fig. 3 Geographical distribution of the population of H. fumariifolia. Population numbers correspond to those in Sosa et al. (2009). Enclosed areas correspond to clades in Fig. 1

Fig. 4 in Refugia and geographic barriers of populations of the desert poppy, Hunnemannia fumariifolia (Papaveraceae)

Fig. 4 Chronogram based on Bayesian approach of the H. fumariifolia phylogeography. Gray bars 95 % confidence intervals for node age estimates. Brackets identify clades as given in Fig 2. Circled letters at

publicNov 2015View details →

Data from: The contemporary genetic pattern of European moose is shaped by postglacial recolonization, bottlenecks, and the geographical barrier of the Baltic Sea

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publicMay 2013View details →

Data from: Geographic population structure of the African malaria vector Anopheles gambiae suggests a role for the forest-savannah biome transition as a barrier to gene flow

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