Genetic diversity of immature Kemp's ridley (Lepidochelys kempii) sea turtles from the northern Gulf of Mexico

Abstract

The Kemp’s ridley (Lepidochelys kempii) is the world’s most endangered sea turtle species. Predominately nesting at only one beach in Mexico, this species declined to an estimated 300 females in the mid‐1980s. Conservation efforts in the United States and Mexico, including a head start programme in southern Texas in which hatchlings were reared in captivity for several months before being released into the wild, resulted in the recovery of this species. Although genetic data have previously been used to assess the success of the head start programme and dispersal of individual adults, data on immature turtles sampled at foraging areas and adult females sampled at the main nesting beach in Mexico are lacking. Genetic characterization of immature individuals is important for understanding recruitment, survival, and population demography, while genetic data on individuals from Mexico are essential for understanding dispersal and overall genetic diversity in this species. To address these gaps, mitochondrial DNA data were collected from 106 immature individuals sampled at four different foraging sites in the northern Gulf of Mexico and from 18 nesting females at the primary nesting beach in Mexico. Two previously unknown mitochondrial DNA haplotypes were discovered among the immature individuals. Except for these two new haplotypes, the genetic diversity of immature individuals in the northern Gulf of Mexico closely corresponds to that of adults sampled in Mexico, which suggests that much of the diversity within the nesting population can be found among immature animals dispersing to foraging grounds, including locations in the northern Gulf of Mexico. Continued monitoring of the genetic variation of different life stages of this species across its distribution range will help assess the success of conservation programmes by ensuring the maintenance of genetic diversity and representation of this diversity across the species’ distribution range.

Confirmation of significant sea turtle nesting activity on a remote island chain in the Gulf of Mexico

“…The Kemp's ridley embryo from the June 24 nest was too badly degraded to provide complete microsatellite data, but all three Kemp's ridley nests (June 8, June 24, July 29_02) yielded control region haplotype Lk1.1 (Genbank KF385935). This haplotype is quite rare in the Texas nesting population (2%, Frandsen et al, 2020 ) and among foraging individuals (4%, Frandsen et al, 2020 ; 2%, Lamont et al, 2021 ), suggesting that all three clutches were likely laid by the same female.…”

“…Over the past two decades, Kemp's ridleys appear to have expanded their nesting range with sporadic nesting documented along the Gulf coast into Florida (Pike, 2013 ; Shaver et al, 2016 ). Recent genetic analyses also suggest the species may be undergoing range expansion (Frandsen et al, 2020 ; Lamont et al, 2021 ). As species undergo range expansion across the globe (Henry III et al, 2021 ), protected areas are being disproportionally settled (Thomas et al, 2012 ).…”

“…Recent genetic analyses also suggest the species may be undergoing range expansion (Frandsen et al, 2020;Lamont et al, 2021).…”

Interspecific interactions among three species of sea turtle using a common resting area

“…Additionally, more aggressive individuals typically win fights over foraging resources, which might also have life‐history consequences for the less aggressive individuals (Schofield et al, 2022 ). These consequences could be serious for all three species but particularly for Kemp's ridleys, whose population is recovering from a severe population bottleneck that occurred in the mid‐1980s (Lamont et al, 2021 ). Genetic diversity of the Kemp's ridley population has not yet recovered from the bottleneck (Lamont et al, 2021 ).…”

“…These consequences could be serious for all three species but particularly for Kemp's ridleys, whose population is recovering from a severe population bottleneck that occurred in the mid‐1980s (Lamont et al, 2021 ). Genetic diversity of the Kemp's ridley population has not yet recovered from the bottleneck (Lamont et al, 2021 ). Low genetic diversity reduces the fitness of a population and the potential of a population to respond to a changing environment (Hoelzel, 1990 ).…”