Recent Demographic Expansion Research Articles

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.

Global phylogeography of the insect pest Callosobruchus maculatus (Coleoptera: Bruchinae) relates to the history of its main host, Vigna unguiculata

AbstractAimThe seed beetle Callosobruchus maculatus is an important tropical and subtropical pest of legumes distributed world‐wide. Archaeological evidence suggests an African origin with later world‐wide invasion facilitated by the last centuries’ legume trading and exchange. To date, no studies could identify the routes or timing of dispersal of the species. Here, we investigate the global phylogeography of this pest to shed light on the main inter‐continental dispersal routes that led to it becoming a cosmopolitan pest.LocationWorld‐wide.MethodsWe sampled seed beetles over a large fraction of the species’ range and sequenced one nuclear and three mitochondrial loci. Using this data, we estimated spatio‐temporal phylogeographical reconstructions, and the demographic history of the species. We also used our dataset to evaluate the effect of panmixia on Bayesian demographic estimations.ResultsCallosobruchus maculatus exhibited regional and continental genetic structure, with the highest genetic diversity found in Africa. Our discrete Bayesian phylogeographical approach indicated that the species first dispersed to Asia and then colonized the pantropical belt. The three methods used for inferring the demographic history of C. maculatus indicated a recent demographic expansion in the world‐wide dataset, as well as in the subset restricted to African samples. Such a signal was, however, not observed in the subset composed of Asian specimens. This demographic expansion occurred in the Holocene and is likely explained by the spread of cowpea and other host legumes across and out of Africa.Main conclusionsThe inferred dispersal routes support the idea that the evolutionary history of C. maculatus relates to the trade of its main host plant, Vigna unguiculata. Human‐mediated processes appear to have shaped the global genetic structure of this pest. As a methodological implication, we demonstrate that coalescent‐based demographic reconstructions can be erroneous if the dataset violates the assumption of panmixia.

Significant genetic differentiation of Gobiopterus lacustris, a newly recorded transparent goby in China

In our recent survey, the transparent small Lacustrine goby, Gobiopterus lacustris had reported as the endemic species of Luzon, Philippines, was identified as an abundant species in mangroves of Leizhou Peninsula, China. Here, high diversity and significant differentiation of five sites of samples representing the west and east populations were revealed by mitochondrial DNA sequences. Five haplotypes of 56 cytochrome oxidase subunit I (Cox1) with the lengths of 623 base pairs (bp) have the high pairwise identity (>98.8%). Moreover, a total of 31 haplotypes for 129 partial D-loop regions were clustered into two clades corresponding to the east and west sampling sites. The strong population structure was confirmed (ΦST = 0.43017, p < .0001) with high haplotype diversity (h = 0.880 ± 0.017) and low nucleotide diversity (p=.00484). Moreover, both the mismatch distribution analysis and neutral test of D-loop revealed that the west group might experience a recent demographic expansion. Lastly, the isolation-with-migration analysis supported the expansion and indicated that the east–west split happened at approximately 7.1 kyr ago. Given the distribution and diversity, G. lacustris could be a good model for the study of the sea-level fluctuations and coast evolution of the South China Sea.

Contrasting evolutionary patterns between two haplogroups of Haematobia exigua (Diptera: Muscidae) from the mainland and islands of Southeast Asia

Uncovering the hidden diversity and evolutionary history of arthropods of medico-veterinary importance could have significant implications for vector-borne disease control and epidemiological intervention. The buffalo fly Haematobia exigua is an obligate bloodsucking ectoparasite of livestock. As an initial step towards understanding its population structures and biogeographic patterns, we characterized partial cytochrome c oxidase subunit I (COI) and cytochrome b (Cytb) sequences of H. exigua from three distinct geographic regions in Southeast Asia. We detected two distinct mitochondrial haplogroups of H. exigua in our surveyed geographic regions. Haplogroup I is widespread in the Southeast Asian mainland whereas haplogroup II is generally restricted to the type population Java Island. Both haplogroups were detected co-occurring on Borneo Island. Additionally, both haplogroups have undergone contrasting evolutionary histories, with haplogroup I exhibited a high level of mitochondrial diversity indicating a population expansion during the Pleistocene era dating back to 98,000 years ago. However, haplogroup II presented a low level of mitochondrial diversity which argues against the hypothesis of recent demographic expansion.

Selection on MHC in a Context of Historical Demographic Change in 2 Closely Distributed Species of Tuco-tucos (Ctenomys australis and C. talarum).

Selection necessarily acts within the same current and historical demographic framework as neutral evolutionary processes, and the outcome of the interplay between these forces may vary according to their relative strength. In this study, we compare the variation at a major histocompatibility complex (MHC) locus (DRB exon 2), typically subject to strong diversifying selection, and mitochondrial diversity (D-loop) across populations encompassing the entire distribution of 2 species of South American subterranean rodents: Ctenomys australis and C. talarum (tuco-tucos). Although these species are parapatric along most of their distribution, historically they have followed distinct demographic trajectories associated with sea level changes during the Quaternary. We surveyed 8 populations of C. australis and 15 of C. talarum, from which we analyzed 70 and 212 D-loop haplotypes and 91 and 346 DRB genotypes, respectively. Both species have gone through a recent demographic expansion; however, the signal of this process only encompasses the entire distribution of one of the species: C. australis. While balancing selection on MHC in C. talarum-enhanced DRB diversity at the local level compared to D-loop, although not promoting divergence among populations, in C. australis local diversifying selection may have driven higher population differentiation at DRB than at D-loop. Our findings reinforce the idea that the relative strength of selection acting on MHC genes varies spatially and temporally within and among species, even between species using the same macrohabitat and exposed to similar immune challenges.

Diversidad y estructura genética de artibeus jamaicensis (chiroptera: phyllostomidae) en Chiapas, México

La deforestación de las selvas provoca la fragmentación de los hábitats, lo cual interviene en la composición, abundancia y demografía de las especies, y por lo tanto, en el aislamiento poblacional en muchas especies. Los impactos de la fragmentación dependerán de la capacidad de respuesta de las especies a los disturbios en su hábitat, y de la configuración y estructura del paisaje. En algunas poblaciones, la fragmentación del hábitat puede provocar el aislamiento poblacional a largo plazo, por la reducción del tamaño poblacional y el debilitamiento de relaciones entre individuos, aún en especies de alta movilidad como los murciélagos. En México, A. jamaicensis es de los murciélagos más estudiados; sin embargo, son pocos los trabajos enfocados en conocer los impactos de la modificación de su hábitat, en su diversidad y estructura genética. Por lo tanto, el objetivo de este trabajo fue evaluar la diversidad, la estructura y la diferenciación genética, así como analizar la historia demográfica de A. jamaicensis en dos hábitats diferentes, utilizando un fragmento de 396 pb de la región mitocondrial D-loop. La red de haplotipos reveló 34 haplotipos únicos de 34 individuos analizados. La diversidad haplotípica fue alta (h = 1) para ambas poblaciones, y la diversidad nucleotídica fue relativamente baja (&lt; 0.03). El análisis de la distribución de diferencias nucleotídicas pareadas (distribución mismatch), y los valores negativos de los estadísticos basados en pruebas de neutralidad, sugieren un proceso de expansión demográfica reciente y repentina de A. jamaicensis. Una moderada diferenciación genética apunta a que existe estructura genética de A. jamaicensis.

Epigean gammarids survived millions of years of severe climatic fluctuations in high latitude refugia throughout the Western Carpathians

Isolated glacial refugia have been documented in Central Europe for a number of taxa, but conclusive evidence for epigean aquatic species has remained elusive. Using molecular data (mitochondrial and nuclear markers), we compared the spatial patterns of lineage diversity of the widely distributed Gammarus fossarum species complex between two adjacent biogeographically and geomorphologically distinct Central European regions: the Bohemian Massif and the Western Carpathians. We investigated if the observed patterns of spatial diversity are more likely to stem from historical or present-day factors. Phylogenetic and phylogeographic analyses revealed eight phylogenetically diverse lineages: two exhibiting local signatures of recent demographic expansion inhabit both regions, while the other six display a relict distributional pattern and are found only in the Western Carpathians. Molecular dating indicates that these lineages are old and probably diverged throughout the Miocene (7–18Ma). Furthermore, their distribution does not seem to be constrained by the present boundaries of river catchments or topography. The contrasting spatial patterns of diversity observed between the two regions thus more likely result from historical rather than contemporaneous or recent factors. Our results indicate that despite the high latitude and proximity to the Pleistocene ice sheets, the Western Carpathians functioned as long-term glacial refugia for permanent freshwater fauna, allowing the uninterrupted survival of ancient lineages through millions of years of drastic climatic fluctuations.

Mitochondrial DNA sequence variation in Iranian native dogs

The dog mtDNA diversity picture from wide geographical sampling but from a small number of individuals per region or breed, displayed little geographical correlation and high degree of haplotype sharing between very distant breeds. For a clear picture, we extensively surveyed Iranian native dogs (n = 305) in comparison with published European (n = 443) and Southwest Asian (n = 195) dogs. Twelve haplotypes related to haplogroups A, B and C were shared by Iranian, European, Southwest Asian and East Asian dogs. In Iran, haplotype and nucleotide diversities were highest in east, southeast and northwest populations while western population had the least. Sarabi and Saluki dog populations can be assigned into haplogroups A, B, C and D; Qahderijani and Kurdi to haplogroups A, B and C, Torkaman to haplogroups A, B and D while Sangsari and Fendo into haplogroups A and B, respectively. Evaluation of population differentiation using pairwise FST generally revealed no clear population structure in most Iranian dog populations. The genetic signal of a recent demographic expansion was detected in East and Southeast populations. Further, in accordance with previous studies on dog-wolf hybridization for haplogroup d2 origin, the highest number of d2 haplotypes in Iranian dog as compared to other areas of Mediterranean basin suggests Iran as the probable center of its origin. Historical evidence showed that Silk Road linked Iran to countries in South East Asia and other parts of the world, which might have probably influenced effective gene flow within Iran and these regions. The medium nucleotide diversity observed in Iranian dog calls for utilization of appropriate management techniques in increasing effective population size.

Population parameters and mito-nuclear mosaicism of Anisakis spp. in the Adriatic Sea

Recombinant genotypes of A. simplex sensu stricto (s.s.) and A. pegreffii, two species of Anisakis simplex complex found in sympatric waters of the Mediterranean Sea, are believed to be a product of interspecific hybridisation and/or DNA introgression. In contrast, such events within an allopatric area as the Adriatic Sea are unlikely to occur and therefore observed recombination should be assessed more closely. We have genotyped 525 anisakids collected from migratory and non-migratory fish of the southern part of the Adriatic Sea, inferring its omniparentage at nuclear (ITS locus) and matrilineage at mitochondrial locus (cox2). The aim was to address the presence and cause of the recombination within the population and to test its genetic structure under admixture theory. Population parameters, i.e. prevalence, and mean abundance and intensity of anisakids were also evaluated to contribute for future epidemiological risk assessments. As a result, we have inferred the presence of A. pegreffii, A. typica and A. ziphidarum in the Adriatic, lacking type species A. simplex s.s. at both nuclear and mitochondrial locus. A. pegreffii population shows a high level of admixture and heterogeneity and a recent demographic expansion from a small population size. We argue that the observed recombinant genotypes in the Adriatic are a product of ancestral polymorphism and consequent remote genetic introgression.

Phylogeography of Hydropuntia cornea/Hydropuntia usneoides complex (Gracilariales, Rhodophyta) in the Yucatan Peninsula

:Phylogeographic studies can contribute to our understanding of the evolutionary forces acting on the patterns of genetic variation and the evolutionary history of species. The Hydropuntia cornea/Hydropuntia usneoides species complex consists of two common species of red algae in the Gulf of Mexico and Caribbean Sea. Both species exhibit high phenotypic plasticity and total overlap in morphological characters and are only distinguished genetically (group GI, assigned to H. usneoides and group GII, assigned to H. cornea). In the Yucatan Peninsula, where they are abundant, they have a sympatric distribution. In order to understand the historical events and their influence on the current distribution patterns of these species around the Yucatan Peninsula and compare them with some populations from Venezuela and Brazil, we analyzed variation in the plastid-encoded RuBisCo spacer. A total of 133 individuals collected from 14 sites were sequenced. The analyses revealed 12 haplotypes (R1–R12). The haplotype network revealed two major groups (GI and GII) separated by three mutational steps. Group I was found in almost all sampled sites (n = 13), while GII was found in six sites but was absent from the Gulf of Mexico (Campeche). Haplotype R1 was the most abundant in GI, and haplotype R4 was dominant in GII. Genetic variation was higher in GI than in GII. Mismatch distribution suggests that GI may be in a period of demographic equilibrium, and GII experienced a recent demographic expansion and may have come from the south when the northern portion of the peninsula emerged (2.8 million years ago). Our results revealed that the Yucatan Peninsula is a mix of southern and northern floristic influences, which can be explained by the geological events in the area.

Population Genetic Structure and Genetic Diversity in Twisted-Jaw Fish,Belodontichthys truncatusKottelat &amp; Ng, 1999 (Siluriformes: Siluridae), from Mekong Basin

The Mekong River and its tributaries possess the second highest diversity in fish species in the world. However, the fish biodiversity in this river is threatened by several human activities, such as hydropower plant construction. Understanding the genetic diversity and genetic structure of the species is important for natural resource management.Belodontichthys truncatusKottelat &amp; Ng is endemic to the Mekong River basin and is an important food source for people in this area. In this study, the genetic diversity, genetic structure, and demographic history of the twisted-jaw fish,B. truncatus,were investigated using mitochondrialcytochrome bgene sequences. A total of 124 fish specimens were collected from 10 locations in the Mekong and its tributaries. Relatively high genetic diversity was found in populations ofB. truncatuscompared to other catfish species in the Mekong River. The genetic structure analysis revealed that a population from the Chi River in Thailand was genetically significantly different from other populations, which is possibly due to the effect of genetic drift. Demographic history analysis indicated thatB. truncatushas undergone recent demographic expansion dating back to the end of the Pleistocene glaciation.

A cryptic mitochondrial DNA link between North European and West African dogs

Domestic dogs have an ancient origin and a long history in Africa. Nevertheless, the timing and sources of their introduction into Africa remain enigmatic. Herein, we analyse variation in mitochondrial DNA (mtDNA) D-loop sequences from 345 Nigerian and 37 Kenyan village dogs plus 1530 published sequences of dogs from other parts of Africa, Europe and West Asia. All Kenyan dogs can be assigned to one of three haplogroups (matrilines; clades): A, B, and C, while Nigerian dogs can be assigned to one of four haplogroups A, B, C, and D. None of the African dogs exhibits a matrilineal contribution from the African wolf (Canis lupus lupaster). The genetic signal of a recent demographic expansion is detected in Nigerian dogs from West Africa. The analyses of mitochondrial genomes reveal a maternal genetic link between modern West African and North European dogs indicated by sub-haplogroup D1 (but not the entire haplogroup D) coalescing around 12,000 years ago. Incorporating molecular anthropological evidence, we propose that sub-haplogroup D1 in West African dogs could be traced back to the late-glacial dispersals, potentially associated with human hunter-gatherer migration from southwestern Europe.

Low genetic diversity and recent demographic expansion in the red starfish Echinaster sepositus (Retzius 1816).

Understanding the phylogeography and genetic structure of populations and the processes responsible of patterns therein is crucial for evaluating the vulnerability of marine species and developing management strategies. In this study, we explore how past climatic events and ongoing oceanographic and demographic processes have shaped the genetic structure and diversity of the Atlanto-Mediterranean red starfish Echinaster sepositus. The species is relatively abundant in some areas of the Mediterranean Sea, but some populations have dramatically decreased over recent years due to direct extraction for ornamental aquariums and souvenir industries. Analyses across most of the distribution range of the species based on the mitochondrial cytochrome c oxidase subunit I gene and eight microsatellite loci revealed very low intraspecific genetic diversity. The species showed a weak genetic structure within marine basins despite the a priori low dispersal potential of its lecithotrophic larva. Our results also revealed a very recent demographic expansion across the distribution range of the species. The genetic data presented here indicate that the species might be highly vulnerable, due to its low intraspecific genetic diversity.

Multilocus Analyses Reveal Postglacial Demographic Shrinkage of Juniperus morrisonicola (Cupressaceae), a Dominant Alpine Species in Taiwan.

Postglacial climate changes alter geographical distributions and diversity of species. Such ongoing changes often force species to migrate along the latitude/altitude. Altitudinal gradients represent assemblage of environmental, especially climatic, variable factors that influence the plant distributions. Global warming that triggered upward migrations has therefore impacted the alpine plants on an island. In this study, we examined the genetic structure of Juniperus morrisonicola, a dominant alpine species in Taiwan, and inferred historical, demographic dynamics based on multilocus analyses. Lower levels of genetic diversity in north indicated that populations at higher latitudes were vulnerable to climate change, possibly related to historical alpine glaciers. Neither organellar DNA nor nuclear genes displayed geographical subdivisions, indicating that populations were likely interconnected before migrating upward to isolated mountain peaks, providing low possibilities of seed/pollen dispersal across mountain ranges. Bayesian skyline plots suggested steady population growth of J. morrisonicola followed by recent demographic contraction. In contrast, most lower-elevation plants experienced recent demographic expansion as a result of global warming. The endemic alpine conifer may have experienced dramatic climate changes over the alternation of glacial and interglacial periods, as indicated by a trend showing decreasing genetic diversity with the altitudinal gradient, plus a fact of upward migration.

Genetic structuring among silverside fish (Atherinella brasiliensis) populations from different Brazilian regions

Estuaries are dynamic environments, key for the survival of innumerous ecologically or economically important fish species. Among these species are Neotropical silversides (Atherinella brasiliensis), which are resident and abundant in Brazilian estuaries and used as a complementary source of income and food for local communities. To better understand silverside populations in Brazil, we evaluated the genetic diversity, structure and demography of fish sampled at six estuaries from the northeastern to the southern coast, using Random Amplified Polymorphic DNA and mitochondrial DNA (D-loop) markers. High haplotype diversities (h ranging from 0.75 to 0.99) were found in all populations except Carapebus, located in Southeast Brazil (h = 0.54). A total of 69 mtDNA haplotypes were found, with Itaparica (Northeast Brazil) and Carapebus presenting only exclusive haplotypes, while some were shared among populations in the South. Strong regional structure was observed, with very high differentiation between Itaparica and Carapebus, as well as among these two populations and the ones from the Southern region (Paranaguá, Conceição, Camacho and Patos). Among southern areas, low/moderate structure was detected. Most populations showed unimodal mismatch distributions indicating recent demographic expansion, while Carapebus presented a multimodal distribution characteristic of a stable or bottlenecked population. Times since possible population expansion were highest in Itaparica (32,500 ya) and Carapebus (29,540 ya), while in the Southern region longest time was observed at Conceição (25,540 ya) and shortest at Patos (9720 ya). In a general manner, haplotype diversities were directly related to times since population expansions; again, Carapebus was the exception, displaying long time since expansion but low diversity, possibly due to a recent bottleneck caused by the isolation and human impacts this lagoon is subject to. Isolation by Distance was significant for Itaparica and Carapebus, and considering the extremely high differentiation of these populations, we suggest that they could be undergoing speciation. To adequately manage and maintain the genetic variability of silversides in Brazilian estuaries, we propose three distinct management units for this species: 1) Itaparica; 2) Carapebus; and 3) Southern Brazil.

Multilocus Phylogeography of the Treefrog Scinax eurydice (Anura, Hylidae) Reveals a Plio-Pleistocene Diversification in the Atlantic Forest.

We aim to evaluate the genetic structure of an Atlantic Forest amphibian species, Scinax eurydice, testing the congruence among patterns identified and proposed by the literature for Pleistocene refugia, microrefugia, and geographic barriers to gene flow such as major rivers. Furthermore, we aim to evaluate predictions of such barriers and refugia on the genetic structure of the species, such as presence/absence of dispersal, timing since separation, and population expansions/contractions. We sequenced mitochondrial and nuclear genetic markers on 94 tissue samples from 41 localities. We inferred a gene tree and estimated genetic distances using mtDNA sequences. We then ran population clustering and assignment methods, AMOVA, and estimated migration rates among populations identified through mtDNA and nDNA analyses. We used a dated species tree, skyline plots, and summary statistics to evaluate concordance between population’s distributions and geographic barriers and Pleistocene refugia. Scinax eurydice showed high mtDNA divergences and four clearly distinct mtDNA lineages. Species tree and population assignment tests supported the existence of two major clades corresponding to northeastern and southeastern Atlantic Forest in Brazil, each one composed of two other clades. Lineage splitting events occurred from late Pliocene to Pleistocene. We identified demographic expansions in two clades, and inexistent to low levels of migrations among different populations. Genetic patterns and demographic data support the existence of two northern Refuge and corroborate microrefugia south of the Doce/Jequitinhonha Rivers biogeographic divide. The results agree with a scenario of recent demographic expansion of lowland taxa. Scinax eurydice comprises a species complex, harboring undescribed taxa consistent with Pleistocene refugia. Two rivers lie at the boundaries among populations and endorse their role as secondary barriers to gene flow.

Determining the extent and direction of introgression between three spruce species based on molecular markers from three genomes with different rates of gene flow

Introgression frequently occurs between closely related plant species when there is incomplete reproductive isolation. However, few studies have been designed to examine the extent and direction of introgression from all three genomes, especially when they have different rates of gene flow. Conifers, in which chloroplast (cp), mitochondrial (mt) and nuclear (nr) genomes show contrasting rates of gene flow, provide a good model in which to carry out such a case study. Here we use data on sequence variation in 18 DNAs from three genomes for 311 individuals of 31 populations to investigate the extent and direction of introgressions between three spruce species in areas where they are sympatrically distributed. We found that one species seem to have introgressions derived from the other two species in areas of sympatric distribution; there were more introgressions from the maternally inherited mtDNA, which has the lowest rate of gene flow, and fewer introgressions from the bi-parentally inherited nrDNA. Further coalescent analysis of nrDNA population genetic data suggested that the species containing introgressions had experienced range expansion in the recent past while there was no such indication for the other two species. Our results support the hypotheses that introgressions occurred more frequently at genetic markers with lower rates of gene flow and that they usually took place from local species towards invading species that had undergone recent demographic expansion.

Genetic diversity and phylogenetic analysis of two Tunisian bivalves (Mactridae) Mactra corallina (Linnaeus, 1758) and Eastonia rugosa (Helbling, 1799) based on COI gene sequences

A partial sequence of mitochondrial cytochrome c oxidase subunit I (COI) was used as a genetic marker for a genetic diversity and phylogenetic analysis (DNA barcoding) of two Mactridae species, Mactra corallina and Eastonia rugosa, collected from the Tunisian coast. These Mactridae species could be distinguished by DNA barcoding techniques and they will be considered as monophyletic clades with the Neighbor-Joining (NJ) tree. The genetic structure detected that E. rugosa presents three haplotypes with a high frequency of HER1 (0.89). However, M. corralina shared 14 haplotypes. The haplotypic diversity (H) was equal to 0.205 and 0.954, respectively, for E. rugosa and M. corallina. While the nucleotide diversity (π) was higher for M. corallina (π=0.0818), the mismatch distribution showed a unimodal curve for E. rugosa (a recent sudden demographic expansion) and a multimodal distribution for M. corallina (size stability).

Population genetic structure and historical dispersal patterns in the subterranean rodent Ctenomys “chasiquensis” from the southeastern Pampas region, Argentina

Gene flow plays an essential role in the evolutionary history of the organisms and helps to identify those historical landscape features that most likely had affected the dispersal patterns. In this work, we assess, using mitochondrial control region DNA sequences, the historical migration patterns and population structure in Ctenomys “chasiquensis”, a highly, vulnerable and endemic subterranean rodent distributed in a very small area from the central part of Argentina. We used Bayesian and maximum likelihood approaches to evaluate the effects of historical gene flow among populations. Moreover, we used Bayesian skyline plots, tests of neutrality and mismatch distributions to assess the potential changes in population size through time. Our analyses show that populations of C. “chasiquensis” are moderate structured at regional level and this population pattern is probably the result of an asymmetric historical gene flow essentially from the South-West to the North-West, further of a recent demographic population expansion in the North-West, in conjunction with an important degree of isolation in some populations over its eastern geographical range. Evidently, historical gene flow seems to have been more frequently on the West. Finally, a close relationship appears to exist between the major climatic episodes occurred during the Late Quaternary in the central region of Argentina and the main historical demographic changes inferred for C. “chasiquensis”. The current distribution of C. “chasiquensis” appear to be a relicts of a more extended historical distribution in the Argentinean Pampas in the Late Pleistocene, with a perceptible population decline at the beginning of the Holocene. In this context, Bayesian demographic inferences showed a small but constant increment of population expansion of this species from approximately 90,000 to 11,000 years BP, after which a period of decrease in population size (that started in the early Holocene and continues nowadays) was observed.

Complementary endozoochorous long-distance seed dispersal by three native herbivorous ungulates in Europe

Herbivorous ungulates are key species in the functioning of terrestrial ecosystems, and their recent demographic and geographic expansion in some temperate regions is likely to influence ecological processes, particularly if we consider plants and the frequency of mobile links among plant populations. In forests, long-distance seed dispersal essentially relies on animal movements. Owing to their ability to cover daily long distances, large herbivorous ungulates are assumed to be important vectors for long-distance seed dispersal (hundreds to thousands of metres). To quantify patterns of seed dispersal, we analysed the paths of roe deer (Capreolus capreolus), red deer (Cervus elaphus) and wild boar (Sus scrofa) which had been equipped with GPS collars. We used seed gut passage times from a recent companion paper (Picard et al., Ecology and Evolution, 2015;5:2621–2632). We combined the animal movements and seed gut passage times to estimate seed dispersal curves for herbivorous ungulates. On average, the forest ungulates might disperse consumed seeds over distances greater than 2km, during a 48-h path in the forest. Maximal dispersal distance was longer for red deer (3.5km) and wild boar (3.2km) than for roe deer (2.0km). By combining high excretion rates and long dispersal distance, wild boar appears to be potentially an efficient seed disperser. Seed dispersal by common herbivorous ungulates is likely to play a crucial role in the today's context of rapid environmental changes such as global warming and landscape fragmentation. Differences in the distribution of seed gut passage times and seasonal distances covered underline the relevance of cross comparative approaches and the complementarity of herbivorous ungulates in long-distance seed dispersal.