Dispersal, habitat differences, and comparative phylogeography of Southeast Asian seahorses (Syngnathidae:Hippocampus)

Abstract

Four distinct phylogeographical patterns across Southeast Asia were observed for four species of seahorse (genus Hippocampus) with differing ecologies. For all species, genetic differentiation (based on cytochrome b sequence comparisons) was significantly associated with sample site (Phi(ST) = 0.190-0.810, P < 0.0001) and with geographical distance (Mantel's r = 0.37-0.59, P < 0.019). Geographic locations of genetic breaks were inconsistent across species in 7/10 comparisons, although some similarities across species were also observed. The two shallow-water species (Hippocampus barbouri and Hippocampus kuda) have colonized the Sunda Shelf to a lesser degree than the two deeper-water species (Hippocampus spinosissimus and Hippocampus trimaculatus). In all species the presence of geographically restricted haplotypes in the Philippines could indicate past population fragmentation and/or long-distance colonization. A nested clade analysis (NCA) revealed that long-distance colonization and/or fragmentation were likely the dominant forces that structure populations of the two shallow-water species, whereas range expansion and restricted dispersal with isolation by distance were proportionally more important in the history of the two deeper-water species. H. trimaculatus has the most widespread haplotypes [average clade distance (D(c)) of nonsingleton haplotypes = 1169 km], indicating potentially high dispersal capabilities, whereas H. barbouri has the least widespread haplotypes (average D(c) = 67 km) indicating potentially lower dispersal capabilities. Pleistocene separation of marine basins and postglacial flooding of the Sunda Shelf are extrinsic factors likely to have contributed to the phylogeographical structure observed, whereas differences among the species appear to reflect their individual ecologies.

Genetic differentiation across eastern Pacific oceanographic barriers in the threatened seahorse Hippocampus ingens

“…Previous studies within Hippocampus spp. (Lourie et al 2005;Teske et al 2003) are largely consistent with this prediction of population structure. However, results from a previous study in H. ingens (Sanders et al 2008) detected no population structure among 4 localities along the Pacific coast based on two mitochondrial gene fragments compared among 19 and 13 specimens separately (Sanders et al 2008).…”

“…Nucleotide diversity h p , and segregating site h s diversity estimates were about half that found in several other species of seahorses (e.g. h p = 0.016 in H. kuda; h p = 0.013 in H. spinosissimus, Lourie et al 2005) (Table 1), and consistent with estimates of diversity in cyt b found in this species by Sanders et al (2008). A single insertion was detected at basepair number 207 of this dataset which falls within the control region at basepair 15,787 in the annotated H. kuda mitochondrial genome available on Genbank (NC-010272.1, Kawahara et al 2008).…”

“…Seahorses are thought to display site fidelity as adults, but dispersal ability in juveniles is largely unknown. There is genetic evidence for limited dispersal in all Hippocampus species that have been previously analyzed in a phylogeographic context (Lourie et al 2005;Teske et al 2003). Nonetheless, after male pregnancy, fully formed juveniles are delivered into the water column and the few that survive seem to rise in the water column to surface waters and float with little mobility in currents for unknown duration (Lourie et al 2004).…”

Extensive Jaw Mobility in Suckermouth Armored Catfishes (Loricariidae): A Morphological and Kinematic Analysis of Substrate Scraping Mode of Feeding

“…Indeed, the reduced functional versatility as a consequence of the extreme morphological specialization in many syngnathids could explain (at least partially, next to fisheries pressure for the pet trade, etc.) the current vulnerable status of many syngnathids, especially the most specialized seahorses (Lourie et al 2005).…”

Development and early life history behaviour of aquarium reared Syngnathus acus (Pisces: Syngnathidae)

“…Along the coasts of the Portuguese mainland, these two species seem mainly con¢ned to estuaries (Re¤ , 1999). Habitat fragmentation and/or long distance colonization, as well as restricted dispersal with isolation by distance have already been pointed out as important forces able to determine the actual geographical distribution of certain seahorse species (Lourie et al, 2005).…”