Search

Aim: Local environmental selection and lineage admixture have long been accepted as important adaptive mechanisms in adjusting widespread taxa to new environments. We studied a pond skater, Gerris latiabdominis, to explore the relative roles played by these two mechanisms in its process of adaptation to heterogeneous landscapes. Location: East Asia. Taxon: Gerris latiabdominis Miyamoto, 1958. Methods: Mitochondrial (COI, COII) and nuclear (ddRAD‐seq) markers were sequenced from 202 individuals. Phylogenetic and phylogeographical analyses were conducted to reveal the population genetic structure. The demographical history was simulated by approximate Bayesian computation (ABC). The single‐nucleotide polymorphisms (SNPs) that may have been subjected to natural divergent selection among the populations were assessed, and the recent migration rates were estimated. Finally, shifts in suitable habitat from the last interglacial (LIG) to the present were predicted through ecological niche modelling (ENM). Results: We found population structures inferred from both mitochondrial and nuclear genomes to be almost coincident and to correspond to temporal or spatial heterogeneity. The early Pliocene splitting event between the northern (NO) and southeastern (SE) groups is consistent with the 'arid belt hypothesis', followed by local environmental selection. Approximate Bayesian computation and gene flow estimation strongly suggested that the southwestern (SW) groups originated from a lineage admixture event between the SE and western (WE) groups and subsequently underwent ongoing gene flow from the SE group during the Pleistocene. The mito‐nuclear discordance pattern in the SW group was probably due to the ancient mitochondrial differentiation. Main conclusion: Our results suggest that both local environmental selection and lineage admixture acted as significant mechanisms of G. latiabdominis adaptation to heterogeneous landscapes in East Asia. Furthermore, this study showed that conclusions based exclusively on mitochondrial data might mislead taxonomic, phylogenetic and phylogeographical studies. [ABSTRACT FROM AUTHOR]

Abstract: Aim: Palaeoclimatic and palaeogeological events have been identified as two main factors that influence the genetic structuring of extant organisms. We studied a montane stream‐dwelling insect, Metrocoris sichuanensis, to explore the relative roles played by these two factors in population genetic connectivity. Location: Sichuan Basin, China. Methods: Mitochondrial (COI, COII, Cytb, 16S) and nuclear (EF‐1α, ITS1) markers were sequenced from 208 individuals. Suitable habitat shifts from the Last Glacial Maximum (LGM) to the present were predicted through fine‐tuned ecological niche modelling (ENM). Phylogenetic and phylogeographical analyses were conducted to reveal the population genetic structure. Intraspecific divergence and expansion times were estimated using beast. Finally, the least cost path (LCP) method coupled with migrate analysis was used to identify possible dispersal corridors and estimate the asymmetric gene flow. Results: Our ENM results suggested that population habitat connectivity did not change both in the LGM and current conditions. Whole haplotypes were separated into four highly supported clades/haplogroups that exhibited strong geographical structure. The splitting events between the four lineages likely date back to the Early Pleistocene. Bayesian skyline plot (BSP) indicated a moderate demographic growth from the LGM to the present. A putative dispersal corridor was detected along the Longmen Mountains thrust belt, with unidirectional gene flow from north to south. Main conclusion: Our findings support the geographical isolation of the genetic lineages and a deep early Pleistocene split in M. sichuanensis. Landscape connectivity analysis incorporating the genetic data and the ENM prediction revealed that population genetic connectivity was strongly associated with stable climatic habitats shaped by complex topography. The drainage system might have assisted the rapid movement of populations along the Longmen Mountains thrust belt. A strategy for researching the population genetic connectivity of narrow endemics, such as M. sichuanensis, in global biodiversity hotspots is proposed and discussed in this paper. [ABSTRACT FROM AUTHOR]