Fine-scale spatial genetic structure across the species range reflects recent colonization of high elevation habitats in silver fir (Abies alba Mill.)

Variation in genetic diversity across species ranges has long been recognized as highly informative for assessing populations’ resilience and adaptive potential. The spatial distribution of genetic diversity, referred to as fine-scale spatial genetic structure (FSGS), also carries information about recent demographic changes, yet it has rarely been connected to range scale processes. We studied eight silver fir (Abies alba Mill.) population pairs (sites), growing at high and low elevations, representative of the main genetic lineages of the species. A total of 1368 adult trees and 540 seedlings were genotyped using 137 and 116 single nucleotide polymorphisms (SNPs), respectively. Sites revealed a clear east-west isolation-by-distance pattern consistent with the post-glacial colonization history of the species. Genetic differentiation among sites (FCT=0.148) was an order of magnitude greater than between elevations within sites (FSC=0.031), nevertheless high elevation populations consistently exhibited a stronger FSGS. Structural equation modeling revealed that elevation and, to a lesser extent, post-glacial colonization history, but not climatic and habitat variables, were the best predictors of FGSG across populations. These results may suggest that high elevation habitats have been colonized more recently across the species range. Additionally, paternity analysis revealed a high reproductive skew among adults and a stronger FSGS in seedlings than in adults, suggesting that FSGS may conserve the signature of demographic changes for several generations. Our results emphasize that spatial patterns of genetic diversity within populations provide complementary information about demographic history and could be used for defining conservation priorities.

Effects of Colonization, Geography and Environment on Genetic Divergence in the Intermediate Leaf-Nosed Bat, Hipposideros larvatus

Determining the evolutionary history and population drivers, such as past large-scale climatic oscillations, stochastic processes and ecological adaptations, represents one of the aims of evolutionary biology. Hipposideros larvatus is a common bat species in Southern China, including Hainan Island. We examined genetic variation in H. larvatus using mitochondrial DNA and nuclear microsatellites. We found a population structure on both markers with a geographic pattern that corresponds well with the structure on mainland China and Hainan Island. To understand the contributions of geography, the environment and colonization history to the observed population structure, we tested isolation by distance (IBD), isolation by adaptation (IBA) and isolation by colonization (IBC) using serial Mantel tests and RDA analysis. The results showed significant impacts of IBD, IBA and IBC on neutral genetic variation, suggesting that genetic variation in H. larvatus is greatly affected by neutral processes, environmental adaptation and colonization history. This study enriches our understanding of the complex evolutionary forces that shape the distribution of genetic variation in bats.

Pleistocene origin and colonization history of Lobelia columnaris Hook. f. (Campanulaceae: Lobelioideae) across sky islands of West Central Africa

We aimed to infer the phylogenetic relationships of populations of Lobelia columnaris using chloroplast genomes and estimate the divergence time to reconstruct its historical colonization on the sky islands of Bioko and Cameroon. Specifically, we aim to answer the following questions: (1) What is the phylogenetic relationship among Bioko Island and Cameroon populations? (2) Are the older populations found on the older sky islands? (3) Does the colonization history reflect the age of the sky islands? We assembled novel plastomes from 20 individuals of L. columnaris from five mountain systems. The plastome data was explored with phylogenetic analyses using Maximum likelihood and Bayesian Inference. The complete plastome size varied from 164,609 bp to 165,368 bp. The populations of L. columnaris have a monophyletic origin, subdivided into three plastome-geographic clades. The plastid phylogenomic results and age of the sky islands indicate that L. columnaris colonized first along the Cameroon Volcanic Line’s young sky islands. The earliest divergent event (1.54 Ma) split the population in South Bioko from those on the mainland and North Bioko. The population of South Bioko was likely isolated during cold and dry conditions in forest refugia. Presumably, the colonization history occurred during the middle-late Pleistocene from South Bioko’s young sky island to North Bioko and the northern old sky islands in Cameroon. Furthermore, the central depression with lowland forest between North and South Bioko is a current geographic barrier that keeps separate the populations of Bioko from each other and the mainland populations. The Pleistocene climatic oscillations led to the divergence of the Cameroon and Bioko populations into three clades. L. columnaris colonized the older sky island in mainland Cameroon after establishing South Bioko’s younger sky islands. The biogeography history was an inverse progression concerning the age of the Afromontane sky islands.

Paths of introduction: Assessing global colonization history of the most successful amphibian invader

International socioeconomic relationships form the background that underlies the history of invasive species. Species with economic value, such as the North American bullfrog (Lithobates catesbeianus), are more likely to become internationally distributed and to be subsequently introduced to non-native areas and, consequently, become more difficult to control. Using population genetics methods, we investigated the invasion pathways, the connectivity among clusters in different countries and the native population of origin of globally introduced bullfrog populations. Throughout the analysis of seven microsatellite nuclear loci, one fragment of the mitochondrial cytochrome b locus, and historical information, four main lineages were identified and analyzed along with previous findings. This species’ capability to colonize several countries from few starting lineages highlights the necessity to control new propagule pressure to ensure successful management programs, as high inbreeding and bottleneck effect seem not to diminish the invasive success of this species. There is a consensus between markers that most areas of South America belong to the same genetic population while populations in Asia have a more complex history of introduction.