Conservation initiatives of Syngnathiformes species in the southern Philippines: What does the mitochondrial DNA signature tell us?

Abstract

Abstract Mitochondrial DNA signatures based on the control region and 12S rRNA gene were used to assess the impact of conservation measures on the effective management of vulnerable Syngnathiformes (seahorses, pipefishes, and allies) species. Results from phylogenetic inference, polymorphism, neutrality indices, haplotype networks and microhabitat information may justify the establishment of distinct management units for different species. For smooth seahorses, Hippocampus kuda was identified as a species complex that formed three clusters with 20 haplotypes. Based on molecular data, these are the first records of Hippocampus capensis and Hippocampus casscsio in the Philippines. High haplotype diversity (h = 28; Hd = 0.943), yet low nucleotide diversity (Pi:0.18095) for polymorphism, suggests minor differences among haplotypes. Neutrality indices calculated using Tajima's D (−2.00774), with P < 0.05 and Fu's Fs (−11.645), were significant. However, both tests were negative, a signature of rapid population expansion from a small effective population size, which could be attributed to past heavy harvests and habitat destruction, as supported by local data. For pipefishes and their allies, there was high haplotype diversity (h = 22; Hd = 0.875) and low nucleotide diversity of Pi: 0.16671. However, neutrality indices calculated using Tajima's D (−1.68518) and Fu's Fs (11.549) were not significant, with P > 0.05, indicating a balancing selection for this population. Results reveal that the recent population expansion of seahorses proves that current conservation measures are effectively safeguarding populations, while balancing selection is maintaining genetic polymorphism in pipefishes and their relatives, making them resilient to changing environments. Moreover, as revealed by haplotype networks, intraspecific variation suggests distinct management for different species. In addition, underwater surveys show an essential association between microhabitats and species' survival, thus encouraging future initiatives regarding habitat protection, especially coral reefs, seagrass beds, sponge gardens, mangrove areas and estuaries.