Abstract
Populations are more effectively managed with information on breeding and dispersal behavior, making the evaluation of these characteristics essential for effective conservation of a species. In the USA, 2 critical habitat units were designated in 2009 for the federally endangered smalltooth sawfish Pristis pectinata. Previous research in the Charlotte Harbor Estuary Unit (CHEU) of critical habitat shows that female smalltooth sawfish are polyandrous and highly philopatric to nursery grounds. However, these characteristics have not yet been examined in a larger area of designated critical habitat: the Ten Thousand Islands/Everglades Unit (TTIEU). We used microsatellite genotypes from 214 juvenile smalltooth sawfish to examine mating and dispersal behavior via sibship analyses and reconstruction of parental genotypes with the program COLONY. Parental reconstruction yielded 71 female and 117 male genotypes. Many females returned to the same region within TTIEU for parturition on a biennial cycle; however, at least 1 female switched parturition sites within TTIEU and at least 2 females produced litters in both TTIEU and CHEU over the study period. The maximum number of pups genetically assigned to 1 female was 12, a number that is consistent with that found for CHEU (8 pups), and within the litter size range reported (7 to 14) for the species. Confirmation of these mating behaviors and reproductive characteristics is important for understanding how the present population uses these protected habitats at different life stages, and for determining future habitat protection and population expansion strategies to restore smalltooth sawfish to previously occupied areas of their range.
Highlights
Mating and dispersal behaviors are critical drivers of genetic variation and its distribution across the landscape
After removing family groups with ≤ 2 pups, a total of 214 genotypes were used to reconstruct parental genotypes; 4 of these 214 genotypes were discovered to be pups born and caught in Charlotte Harbor Estuary Unit (CHEU), which we left in subsequent analyses as a negative test for regional philopatry
We found that female smalltooth sawfish (n = 24 reconstructed genotypes) were regionally philopatric to the Ten Thousand Islands/Everglades Unit (TTIEU) for parturition, returning to the same location (e.g. Chokoloskee Bay) or area (e.g. Everglades National Park (ENP)) to give birth, a result consistent with CHEU smalltooth sawfish (Feldheim et al 2017)
Summary
Mating and dispersal behaviors are critical drivers of genetic variation and its distribution across the landscape. Information about these key behaviors is needed to implement effective management strategies for species conservation (Waples 1991, Fraser & Bernatchez 2001). Any threats that negatively affect dispersive males and/or areas where females give birth would affect genetic diversity in the species. This means that threats imposed on the dispersing sex may prevent gene flow into adjacent populations, increasing differentiation, which the mating strategy may not be able to balance. An evaluation of mating strategy and sex differences in dispersal behavior is essential for effective management, mitigation of threats, and conservation of genetic diversity necessary for adaptation
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