David Aurioles Gamboa

The effective size of a population (Ne), which determines its level of neutral variability, is a key evolutionary parameter. Ne can substantially depart from census sizes of present-day breeding populations (NC) as a result of past demographic changes, variation in life-history traits and selection at linked sites. Using genome-wide data we estimated the long-term coalescent Ne for 17 pinniped species represented by 36 population samples (total n = 458 individuals). Ne estimates ranged from 8,936 to 91,178, were highly consistent within (sub) species and showed a strong positive correlation with NC (R2 adj I= 0.59; P = 0.0002). Ne/NC ratios were low (mean, 0.31; median, 0.13) and co-varied strongly with demographic history and, to a lesser degree, with species’ ecological and life-history variables such as breeding habitat. Residual variation in Ne/NC, after controlling for past demographic fluctuations, contained information about recent population size changes during the Anthropocene. Specifically, species of conservation concern typically had positive residuals indicative of a smaller contemporary NC than would be expected from their long-term Ne. This study highlights the value of comparative population genomic analyses for gauging the evolutionary processes governing genetic variation in natural populations, and provides a framework for identifying populations deserving closer conservation attention.

Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) were measured in muscle–blubber biopsy samples from 21 Galapagos sea lion (Zalophus wollebaeki) pups that were live captured in the Galapagos Islands (Ecuador) using gas chromatography/high resolution mass spectrometry. Only traces of PBDEs were detected in one male pup, whereas PCDDs and PCDFs were not detected in any sample. The total concentration of PCBs (SPCB) in the pups averaged 104 mg/kg lipid (range, 49–384 mg/kg). No statistically significant differences in SPCB were observed among the four study sites in the Galapagos Islands. Concentrations of PCB congeners
in Galapagos sea lion pups were dominated by low-molecular-weight congeners. These results suggest that global transport is the main source for PCBs in Galapagos sea lions. The SPCB levels were below immunotoxic and endocrine-disruption thresholds in pinnipeds, suggesting a limited risk of adverse health effects. The present study indicates that Galapagos sea lions can serve as a useful sentinel of pollutants with a long-range transport capacity and that Galapagos Islands are not exempt from the threats of global pollutants despite
its remote locale.

In recent years, more than 130 extinctions have been estimated to have occurred in the marine realm. Here we review this body of evidence and show that this figure may actually be overestimated by as much as 50%. We argue that previous estimates have not fully taken into account critical uncertainties such as naturally variable geographical distributions, and have misinterpreted documentary evidence. However, current evidence indicates that some sharks, rays and reef-associated species, although not necessarily geographically restricted, are particularly vulnerable to anthropogenic impacts and now occur in very low numbers. Overestimating extinctions is of concern because it could reduce confidence in the credibility of the ‘extinct’ category in threatened species lists and, ultimately, be used to question the integrity of conservation and management policies. We suggest that when integrating
future checklists of marine extinct species, there needs to be a more rigorous use of the terminology of extinction, and participation by specialists in each of the particular taxonomic groups involved.

During the 1989 breeding season of the pelagic red crab or langostilla (Pleuroncodes planipes), several samples were taken to quantify the degree of sexual dimorphism of this species off the Pacific coast of Baja California. A total of 881 individuals (493 males and 388 females) were measured for characteristics that could suggest sexual differences. Standard carapace length (cephalotorax length, LEC) was used to standardize the allometric differences in the following characters: maximum carapace width (AC), cheliped length (LQ), maximum cheliped width (AQ), and fresh weight (P) (after freezing). Data were ordered for each millimeter class from 17 to 32 mm LEC (which included juveniles and adults). Differences in allometric growth were analyzed by regression with three models: linear, exponential, and multiplicative. The characteristics that showed sexual dimorphism were as follows: carapace width indicated for males a positive allometric growth (r = 0.79; 99% significance) and for females a lack of growth (r = 0); cheliped growth was positive in males (r = 0.69) and negative in females (r = -0.93); cheliped width in males increased with size (r = 0.88), while in females it decreased (r = -0.44). All these regressions fit well in the linear model. For fresh weight. the multiplicative model was slightly better: males increased in weight more rapidly than did females. However, as expected, both sexes increased in weight (r = 0.98 and 0.97, respectively). In males, positive allometric growth wa observed for length and width of chelipeds, carapace width, and weight; except for weight, this
contrasts with female ,and uggests that selective agent favor differential growth in males. Breeding behavior (male-male competition) could be selecting slightly stronger males (i.e., tho e having larger and wider chelipeds) better able to hold and fertilize a larger number of females.