Return of the ghosts of dispersal past: historical spread and contemporary gene flow in the blue sea star <I>Linckia laevigata</I>

Abstract

AbstrAct.-Marine animals inhabiting the Indian and Pacific oceans have some of the most extensive species ranges in the world, sometimes spanning over half the globe. These Indo-Pacific species present a challenge for study with both geographic scope and sampling density as limiting factors. Here, we augment and aggregate phylogeographic sampling of the iconic blue sea star, Linckia laevigata Linnaeus, 1758, and present one of the most geographically comprehensive genetic studies of any Indo-Pacific species to date, sequencing 392 base pairs of mitochondrial cOI from 791 individuals from 38 locations spanning over 14,000 km. We first use a permutation based multiple-regression approach to simultaneously evaluate the relative influence of historical and contemporary gene flow together with putative barriers to dispersal. We then use a discrete diffusion model of phylogeography to infer the historical migration and colonization routes most likely used by L. laevigata across the Indo-Pacific. We show that estimates of genetic structure have a stronger correlation to geographic distances than to "oceanographic" distances from a biophysical model of larval dispersal, reminding us that population genetic estimates of gene flow and genetic structure are often shaped by historical processes. While the diffusion model was equivocal about the location of the mitochondrial most recent common ancestor (MrcA), we show that gene flow has generally proceeded in a step-wise manner across the Indian and Pacific oceans. We do not find support for previously described barriers at the sunda shelf and within cenderwasih bay. rather, the strongest genetic disjunction is found to the east of cenderwasih bay along northern New Guinea. These results underscore the importance of comprehensive range-wide sampling in marine phylogeography.

Genetic Population Structure of the Coral Reef Sea Star Linckia laevigata in the Western Indian Ocean and Indo-West Pacific

“…laevigata populations due to sea level fluctuations in the Pleistocene [9, 14, 21, 33, 34]. However, these previous studies could not provide a full phylogeographic context of L .…”

“…The AMOVA for the combined data sets revealed a strong genetic structure (Φ ST = 0.13, P < 0.001), comparable with other studies on L . laevigata in the Indo-West Pacific [21, 33]. Moreover, the strong genetic differentiation in the Indo-West Pacific has also been shown in other species, such as the giant tiger prawn Penaeus monodon [50, 66], the crown-of-thorn sea star Acanthaster planci [67], and the holothurians Holothuria atra and Holothuria nobilis [68–69].…”

“…Haptosquilla pulchella , with a long-distance dispersal capacity, shows strong genetic structure among Indo-West Pacific populations, while Haliotis asinina displays high levels of gene flow, despite having a restricted PLD [19, 17]. The existing discrepancy between gene flow and PLD proves that gene flow or connectivity among marine populations is not only affected by larval behaviour, but also by ocean currents [20], topographic features, local adaptation [17], geographical distance [21], and interactions with other species [19]. …”

“…Although several studies have been performed on Linckia laevigata across the Indo-Pacific [9, 21, 24, 33], none has studied gene flow within the WIO. Therefore, to complement previous work on connectivity in Linckia laevigata , the present study investigates the genetic population structure, genetic diversity and historical demography of L .…”

Magnificent dimensions, varied forms, and brilliant colors: the molecular ecology and evolution of the Indian and Pacific oceans

“…These include corals (concepcion et al 2014, Marti-Puig et al 2014), giant clams (Deboer et al 2014a, lobsters (Iacchei et al 2014), and a number of echinoderms (crandall et al , Liggins et al 2014(crandall et al , skillings et al 2014. Vertebrates are represented by sharks (Giles et al 2014), and a wide spectrum of bony fishes including sardinella (Willette et al 2014b), tuna and mackerel (Jackson et al 2014), and a veritable school of reef fishes (bernardi et al 2014, raynal et al 2014, szabo et.…”