Isolation on a remote island: genetic and morphological differentiation of a cosmopolitan odonate

Abstract

Although low levels of genetic structure are expected in highly widespread species, geographical and/or ecological factors can limit species distributions and promote population structure and morphological differentiation. In order to determine the effects of geographical isolation on population genetic structure and wing morphology, 281 individuals of the cosmopolitan odonate Pantala flavescens were collected from four continental (Central and South America) and five insular sites (Polynesian islands and the Maldives). COI sequences and eight microsatellite loci were used to characterize genetic diversity and genetic structure between and within locations. Linear and geometric morphometry were used to evaluate differences in the size and shape of wings. Genetic analysis showed a global genetic difference between the continental and insular sites. American locations did not show genetic structure, even in locations separated by a distance of 5000 km. Easter Island showed the lowest values of genetic diversity (mainly mitochondrial diversity) and the highest values of genetic differences compared to other insular and continental sites. Individuals from Easter Island showed smaller forewings, a different abdomen length to thorax length ratio, and a different configuration of anal loop in the hindwings. Thus, the greater isolation, smaller area, and young geological age seem to have determined the genetic and morphological differences in P. flavescens of Easter Island, where selection could promote a loss of migratory behavior and may improve other life history traits, such as reproduction. This work provides new insight into how microevolutionary processes operate in isolated populations of cosmopolitan species.

Dispersal Reduction: Causes, Genomic Mechanisms, and Evolutionary Consequences

“…These two causes may act in isolation, or jointly. The most paradigmatic examples of secondary reductions in dispersal ability have been associated with the colonisation of islands [13,41], and dispersal reduction is indeed one of the most frequently-invoked insular syndromes. Due to the isolated nature of islands, and other patchy ecosystems (e.g.…”

Evidence for widespread gene flow and migration in the Globe Skimmer dragonfly Pantala flavescens

“…Similarly, Alvial et al (2017) found a lack of population structure between samples from across South and Central America using both mitochondrial and nuclear DNA markers. In contrast, a subsequent study by Alvial et al (2019), which compared samples not only from Central and South America but also from islands in the Pacific and Indian Oceans, did find some suggestion of population structure between 'continental' and 'insular' samples using microsatellite loci, which also suggested that individuals from Rapa Nui formed a genetically distinct population. In addition, Pfeiler & Markow (2017) reanalysed published data (Low, 2017;Troast et al 2016) and suggested that 'concluding global panmixia in P. flavescens may be premature.'…”

“…The ability of P. flavescens to migrate such long distances is facilitated by a unique combination of morphological characteristics. These include distinct wing morphology (Alvial et al, 2019;Li et al, 2014;Moore, 1993;Sacchi & Hardersen, 2013;Suárez-Tovar & Sarmiento, 2016;Outomuro & Johansson, 2019;Zhao, 2012), of which the most obvious adaptation is their enlarged hind wing bases (a feature associated with gliding, Corbet, 1999), as well as unique thoracic musculature (Bäumler et al, 2018). Physiological features that allow individuals to migrate long distances likely involve their ability to make efficient use of lipids as fuel rather than carbohydrates (e.g., Kallapur & George, 1973); it has been suggested that dragonfly fat reserves can sustain eight hours of flapping flight.…”

The first complete mitochondrial genome of the migratory dragonfly Pantala flavescens Fabricius, 1798 (Libellulidae: Odonata)

“…The exceptional ability for long-distance migration (possibly related to passive dispersal mediated by human transport or wind) explains why P. flavescens is even present on one of the world's most remoted islands, the Easter Island, Chile (Samways and Osborn 1998). The analysis of whole mitogenomes from migratory as well as resident P. flavescens populations would be a promising approach to further study the genetic pathways linked to the migratory behavior in this species and would substantially extend insights gained from previous single marker gene analyses (Troast et al 2016;Alvial et al 2019). We here report on the first mitogenome of P. flavescens from a migratory population in Tanzania.…”

“… 2016 ; Alvial et al. 2019 ). We here report on the first mitogenome of P. flavescens from a migratory population in Tanzania.…”