Abstract

We used landmark-based geometric morphometric methods to describe patterns of body shape variation and shape covariation with size among populations of the threatened White Sands Pupfish (Cyprinodon tularosa), a species that occurs in dissimilar aquatic habitats. White Sands Pupfish populations include two genetically distinct, native populations that have been historically isolated in Salt Creek, a saline river, and Malpais Spring, a brackish spring. In addition, two populations were established approximately 30 years before this study by translocation of fish from Salt Creek to Lost River (a saline river) and Mound Spring (a brackish spring). We found significant body shape variation among populations and between males and females. Body shapes were more slender for females than for males and more slender for saline river populations than brackish spring populations. Introductions of pupfish to new habitats resulted in significant departures in body shape and shape allometry from the native Salt Creek population. Shape divergence was more pronounced for the Mound Spring population, which is consistent with a greater change in abiotic conditions. Although Mound Spring pupfish, like Malpais Spring pupfish, were more deep-bodied than saline river pupfish, differences in body shape and the level of sexual dimorphism were significant between the two brackish spring populations, indicating that deep-bodied shapes may be achieved from different anatomical configurations. The significant shape divergence of introduced populations warrants consideration for the conservation of this rare species, as creation of refuge populations for native stocks is a current management strategy.

Abstract

Animals that are unable to meet their metabolic needs should adopt compensatory behaviors to mitigate their energetic deficits. Voluntary hypothermia is one such energy-saving strategy. Physiological constraints associated with the digestion of plant tissues, however, may limit the thermoregulatory options of herbivorous ectotherms. In this laboratory study, selected body temperatures of Desert Iguanas (Dipsosaurus dorsalis), subjected to two different rations of a carnivorous and a herbivorous diet, were measured in a laboratory thermal gradient. Lizards fed a carnivorous diet and rationed to 50% of their daily energetic requirement selected significantly lower body temperatures than did lizards in the other diet/ration treatments. Lizards fed a herbivorous diet selected higher body temperatures than did the same lizards fed a carnivorous diet regardless of ration. Our study indicates that selected temperatures are influenced by both diet quality and quantity. These results support the hypothesis that herbivorous reptiles require elevated body temperatures to digest plant tissues. Our findings do not fully support the behavioral hypothermia hypothesis, which posits that diurnal lizards will seek cool temperatures at night to reduce their energy expenditure. Thermoregulatory strategies of Desert Iguanas and other herbivorous lizards may be influenced by the need to balance high body temperatures to digest plant material with the high metabolic costs of maintaining high temperatures.

Abstract

Genetic variation at 22 nuclear-encoded loci (21 microsatellites and one anonymous locus) and at mitochondrial (mt)DNA was examined among 40 Cape Fear Shiners (Notropis mekistocholas) sampled from the third generation of offspring raised in captivity and among 44 individuals sampled from the “wild” population from which the captive stock was originally constituted. Levels of genetic diversity in both samples were high as compared to other freshwater fishes. However, lower genetic diversity, as reflected by lower number of alleles and gene diversity (nuclear-encoded loci) and number of haplotypes and nucleon diversity (mtDNA), was found in the captive population. Kinship analyses revealed 101 significant half-sib and full-sib relationships in the sample from the captive population versus 83 in the sample from the wild population. Polygynous matings were suggested by the occurrence of 51 significant half-sib relationships that did not share mtDNA haplotypes; polyandrous matings also may have occurred but could not be inferred reliably from the analysis. Effective population size, estimated using a linkage disequilibrium approach, was 49 (95% CI: 43–56) for the captive population and was ∼10 times smaller than that estimated for the wild population 528 (273–5336). Considering the low number of founders (31) originally used to constitute the captive stock, the estimate for the captive population indicates that a high proportion of the adults present at each generation actually contributed to the offspring. This suggests that relatively large effective population sizes may be achieved in captive populations of N. mekistocholas provided a large number of breeding adults are used.

THE LIVING MARINE RESOURCES OF THE WESTERN CENTRAL ATLANTIC. K. E. Carpenter (ed.). 2003 (dated 2002). FAO Species Identification Guide for Fishery Purposes and American Society of Ichthyologists and Herpetologists, Special Publication 5. ISSN 1020 6686. Nonmembers Price $120.00 (plus shipping and handling); Members Price $100.00 (plus shipping and handling). Available from ASIH Special Publications, Allen Marketing and Management, P.O. Box 1897, Lawrence, Kansas 66044. Fax: 785-843-1274. tcandelaria@allenpress.com.—This long-awaited three-volume publication, covering the fishes and fishlike vertebrates, sea turtles, marine mammals, and major invertebrate groups in the Western Central Atlantic Ocean (FAO fishing area 31), is another in

A New Species of the Banjo Catfish Genus Ernstichthys (Siluriformes: Aspredinidae) from the Bermejo River Drainage, La Plata Basin, Argentina

Gastón Aguilera,

Guillermo E. Terán,

Alejandro Méndez-López,

Martín Miguel Montes, and

Tiago P. Carvalho

Systematics of the Neotropical Catfish Genera Nemuroglanis Eigenmann and Eigenmann 1889, Imparales Schultz 1944, and Medemichthys Dahl 1961 (Siluriformes: Heptapteridae)