Intraspecific variation in Anolis sagrei mirrors the adaptive radiation of Greater Antillean anoles

Anolis lizards of the Greater Antilles represent one of the classic examples of vertebrate adaptive radiation. The same morphological types ('ecomorphs') have evolved repeatedly in response to similar ecological pressures on different islands. We tested whether patterns of within species diversification were congruent with between species patterns and the processes leading to the adaptive radiation of Greater Antillean anoles by measuring variation in performance-related morphological characters in the brown anole, Anolis sagrei . We measured morphological and genetic variation in two different habitat types on each of five islands in the Bahamas. We estimated population structure and rates of gene flow within and among islands using eight microsatellite markers. Intraspecific variation in performance-related morphological characters was similar to the pattern of interspecific variation that characterizes the adaptive radiation of this group in the Greater Antilles. For example, limb length was correlated with perch diameter within A. sagrei as has also been shown among species of anole. Morphological divergence in traits has occurred despite relatively high levels of gene flow both within and among islands. These results are discussed in the context of the divergence-with-gene-flow model of speciation. The results provide important intraspecific evidence that the diversification of anoles has been shaped by natural selection and show how ecologically-based selection pressures explain diversification at both the population and species levels.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 189–199.     

Ultrastructure of the Peritrich Ciliate Ambiphrya ameiuri and Its Attachment to the Gills of the Catfish Ictalurus punctatus1

Ambiphrya ameiuri is an ectocommensal peritrich that attaches to the gills of warm-water fishes and filters bacteria from the water. The ultrastructure of this protozoon, its attachment to the fish gills, and its effect on the gill tissue were investigated by scanning and transmission electron microscopy. The peritrich attached to the gills by fibers extending from the scopula. A microtubular array, apparently a barren kinetosome, was present in each lobular projection, but no scopular cilia were observed. At low densities Ambiphrya had no apparent harmful effects on the fish; however, at high densities respiration may be impeded. Ultrastructural studies indicate that this organism receives no nourishment from the host tissue.     

Development and Validation of a Wing Key to Improve Harvest Management of Alcids in the Northwest Atlantic

Abstract: Murres (thick-billed [Uria lomvia] and common [U. aalge]) are legally hunted along the coast of Newfoundland and Labrador, Canada. Razorbills (Alca torda) are also incidentally taken. Only irregular estimates of the total murre harvest are available, so a tool to derive estimates of age- and species-specific harvest is required to effectively monitor the hunt and manage a sustainable harvest. We collected 293 murre and razorbill wings from hunters between 1999–2004, with the goal of identifying wing characteristics that could be used to discriminate age and species. We found that murres and razorbills could be reliably aged (first-yr vs. older) on the basis of molt limits of greater wing coverts. Using a discriminant function (DF) incorporating length of the first primary and second secondary feather, we classified 95–96% of common murres and 99–100% of thick-billed murres correctly to species. First-year thick-billed and common murres also differed in number of pale secondary coverts (median = 12 and 3, respectively), providing another species-specific trait. We developed a key to age and assign species based on these results. We assessed applicability and accuracy of the wing-key with novice observers, who differentiated between murre and razorbill wings using feather-pattern coloration with high accuracy (95 ± 9%) and were able to differentiate between the 2 murres species using 3 techniques: visual assessment of wing shape (83 ± 14% accuracy), the DF (94 ± 6%), and number of worn secondary coverts for first-year birds only (83 ± 5%). Experience increased success rates of aging and species classification using wing shape and number of worn secondary coverts but not using the DF. Despite differences in measurement accuracy and repeatability among observers, the DF proved to be robust. Our results will facilitate implementation of a species composition survey for the murre hunt and will improve identification rates of carcasses found during beached bird surveys in the Northwest Atlantic, aiding in monitoring of alcid populations vulnerable to anthropogenic activities.     

Evolution of intraspecific variation in the advertisement call of a cricket frog (Acris crepitans, Hylidae)

Advertisement calls of the cricket frog, Acris crepitans , show statistically significant variation among populations in all call variables measured. Call variables show strong clinal variation resulting in calls of lower frequency, longer duration and slower call rates produced by A. c. blanchardi in open habitat in the west of the range, and calls of higher frequency, shorter calls and faster call rates produced by A. c. crepitans in the pine forests in the eastern part of the range. This clinal variation does not result from pleiotropic effects of body size or any other morphological characters we measured.
The two subspecies usually reside in different habitats, but some A. c. blanchardi reside in an isolated pine forest in central Texas. By comparing the calls of this subspecies in open and forest habitat, and by statistically removing the effects of clinal variation for all populations, we determined that habitat explains some of the variation in call structure; this is not true of subspecies.
Our data reject several hypotheses that purport to explain the evolution of mate recognition signals. (1) We reject the notion of Paterson and others that there is strong stabilizing selection on species-specific mate recognition signals. (2) There is no support for the hypothesis that call variation is primarily due to pleiotropic effects of body size or other morphological characters over the geographic range we examined. (3) There is no evidence for reproductive character displacement. (4) Our data, as well as experimental studies of habitat acoustics, support the hypothesis that some differences in calls among habitats result from environmental selection on call structure to enhance call transmission. We suggest that the latter hypothesis does not explain the strong clinal component of call variation. This might result from the passive effects of gene flow between populations at the extremes of the range under selection generated by habitat acoustics.