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

Abstract

Understanding the population structure and evolutionary history of the eastern Pacific seahorse Hippocampus ingens is critical for the effective management of this threatened species. Life history characteristics of H. ingens (site fidelity and brooding of young) may limit gene flow and lead to population differentiation. A recent study analyzing conserved fragments of the mitochondrial cyt b and control region found no population structure. We re-assess this conclusion with a phylogeographic analysis of relationships among 115 individuals of H. ingens over a broader geographic range (San Diego Bay in California, Gulf of California, Central America, Ecuador, and Peru) based on a more variable 428 base pair fragment of the control region. This expanded analysis affirms low overall nucleotide diversity relative to other seahorses (h p = 0.004), and shows evidence of a recent bottleneck and population expansion since the middle Pleistocene. AMOVA analysis shows moderate overall population structure (U ST = 0.10, P val = 0.00), and pairwise U ST estimates indicate structure between the Gulf of California and all Pacific coast localities. Knowledge of population structure in H. ingens may improve conservation efforts by identifying evolutionarily important management units, and could determine source regions in the continuing trade of seahorses for traditional Chinese medicine. The level of genetic divergence observed between the Gulf of California and all other localities sampled may distinguish the Gulf as a separate management unit. Additional phylogeographic research with more quickly evolving genetic markers and targeted sampling at the mouth of the Gulf of California is warranted to inform strategies for conservation of this threatened seahorse.

Historical and contemporary population genetic connectivity of the European short‐snouted seahorse Hippocampus hippocampus and implications for management

“…Populations of H. hippocampus were defined by high haplotypic diversity and low nucleotide diversity, a pattern observed in other seahorse species (Teske et al , 2003; Saarman et al , 2010). The European population of H. hippocampus displays a genetic pattern typical of a population that has undergone a recent (in geological terms) expansion in both numbers and range: one common haplotype present across the range, most (83·1%) haplotypes unique to single sites, and a shallow star‐like pattern of genetic relatedness among haplotypes.…”

DNA barcoding reflects the diversity and variety of brooding traits of fish species in the family Syngnathidae along China’s coast

“…The mean intraspecific genetic distance ranged from 0.15% to 1.57% for the entire data set. Biological mechanisms, water dynamics (such as ocean currents), geographic distance, and historical events may play important roles in the population genetic structures of marine species (Barber et al, 2000;Nelson et al, 2000;Saarman et al, 2010). Many marine fish lack a phylogeographic structure and show genetic homogeneity within populations (Friess and Sedberry, 2011; Zhang et al, 2014).…”

Genealogical approaches to the temporal origins of the Central American gap: Speciation and divergence in Pacific <i>Chthamalus</i> (Sessilia: Chthamalidae)

“…Robertson & Cramer (2009) note that because the appearance of the CAG as a "distinctive entity" in their analysis is in part because of an absence of data, rather than information on the potential for migration or gene flow across the region, additional range-wide genetic analysis of fish and other taxa is warranted. The small number of population genetic studies that span this region suggest there are many cryptic populations along the TEP coast (Hellberg 1998, Arnaud et al 2000, Díaz-Jaimes et al 2006, Wares et al 2009, Saarman et al 2010, and in many cases the break in diversity could be spatially associated with the CAG (Díaz-Jaimes et al 2006, Hurtado et al 2007, Pitombo & Burton 2007. in the intertidal snail Nerita, two species are known to span this region; one exhibits a strong break while the other does not (Hurtado et al 2007), suggesting that knowledge of both habitat and interactions between life history, behavior, and physical oceanography may be necessary to predict the effect of this habitat break on coastal diversity.…”