Limited dispersal and local adaptation promote allopatric speciation in a biodiversity hotspot

Abstract

Recently diverged or diverging populations can offer unobstructed insights into early barriers to gene flow during the initial stages of speciation. The current study utilised a novel insect system (order Mantophasmatodea) to shed light on the early drivers of speciation. The members of this group have limited dispersal abilities, small allopatric distributions and strong habitat associations in the Cape Floristic Region biodiversity hotspot in South Africa. Sister taxa from the diverse family Austrophasmatidae were chosen as focal species (Karoophasma biedouwense, K. botterkloofense). Population genetics and Generalized Dissimilarity Modelling (GDM) were used to characterise spatial patterns of genetic variation and evaluate the contribution of environmental factors to population divergence and speciation. Extensive sampling confirmed the suspected allopatry of these taxa. However, hybrids were identified in a narrow region occurring between the species' distributions. Strong population structure was found over short geographic distances; particularly in K. biedouwense in which geographic distance accounted for 32% of genetic variation over a scale of 50 km (r = .56, p < .001). GDM explained 42%–78% of the deviance in observed genetic dissimilarities. Geographic distance was consistently indicated to be important for between species and within population differentiation, suggesting that limited dispersal ability may be an important neutral driver of divergence. Temperature, altitude, precipitation and vegetation were also indicated as important factors, suggesting the possible role of adaptation to local environmental conditions for species divergence. The discovery of the hybrid‐zone, and the multiple allopatric species pairs in Austrophasmatidae support the idea that this could be a promising group to further our understanding of speciation modes.

The past, present, and future of ecogeographic isolation between closely related Aquilegia plants

“…For example, sympatry among sister taxa has higher range overlaps than non‐sister congener comparisons (Anacker & Strauss, 2014; Grossenbacher et al, 2014). Alternatively, the dispersal capacity of a given species and interactions with predators, competitors, and mutualists may also strongly affect its ecological niche, species range, and the resulting ecogeographic isolation (Barvea et al, 2011; Dool et al, 2022).…”

“…given species and interactions with predators, competitors, and mutualists may also strongly affect its ecological niche, species range, and the resulting ecogeographic isolation (Barvea et al, 2011;Dool et al, 2022).…”

Integrating Genomics, Collections, and Community Science to Reveal Speciation in a Variable Monitor Lizard (Varanus tristis)

“…GDM uses I-spline functions to perform non-linear regression between pairwise matrices (Ferrier et al 2007). The approach has been extensively used to analyze community dissimilarity but has also gained popularity as a way to identify the drivers of genetic differentiation (e.g., Myers et al 2019; Dool et al 2022). We performed the analyses on the gdm v1.5.0.1 R package (Fitzpatrick et al 2021).…”

Ensemble modelling of Pirarucu (Arapaima gigas) distribution in biodiversity hotspot to understand its invasion risk

“…Biodiversity hotspots are designated geographical areas with exceptionally high species diversity and endemism and are at risk of degradation and destruction (Mittermeier et al, 1999; Myers, 1990; Myers et al, 2000; Reid, 1998). Such areas provide numerous ecological services and act as a cradle for speciation (Dool et al, 2022; Latimer et al, 2005; Pereira et al, 2013; Rix et al, 2015). Through intricate ecological interactions between species and their environment, these regions maintain an ecological equilibrium.…”