Rusty A. Gonser

SPATIAL DYNAMICS OF ALTERNATIVE REPRODUCTIVE STRATEGIES: THE ROLE OF NEIGHBORS

In territorial species, the reproductive success of a male is dependent on the quality of his territory. One important component of territory quality is spatial location. High-quality territories not only should be located in areas of high food abundance and low predation, but also should be located in areas that offer optimal amounts of social interaction. Such optima might be different for individuals according to their sex, domi- nance, or genotype. We studied territory quality (size, vegetation structure, and placement) in a socially monogamous, polymorphic passerine, the White-throated Sparrow (Zonotrichia albicollis), in order to determine how spatial attributes contribute to selection intensity on two genotypes. In this species, plumage (white and tan), behavior, and life-history char- acteristics have a genetic basis and are correlated with the presence or absence of a chro- mosomal inversion. Using remote sensing and Geographic Information Systems (GIS), we found that the territories of white and tan males do not differ in size or vegetation structure, suggesting that these factors are not of primary importance to males when deciding where to establish a territory. Instead, we suggest that the placement of white and tan territories depends on the number of neighbors (particularly, white male neighbors). Tan males settle in low-density, neighbor-restrictive habitats where intruder pressure from white males seek- ing extra-pair copulations is reduced. In contrast, white males tend to settle in high-density areas where the probability of encountering neighboring fertile females is greatest. This segregation has led to intraspecific niche partitioning in the two disassortative pair types so that each male morph can best exploit its respective reproductive strategies. These factors may, in turn, contribute to the maintenance of this unusual mating system and, ultimately, the stability of the polymorphism in this species. Similar forces may be operating in other species without distinct morphological markers; we suggest that researchers keep social factors in mind when examining habitat selection.

Spectral analysis of coastal vegetation and land cover using AISA + hyperspectral data

This paper describes a spectral analysis of several coastal land cover types in South Padre Island, Texas using AISA+ hyperspectral remote sensing data. AISA+ hyperspectral data (1.5 metre) were acquired throughout the area on 9 March 2005. Data over mangrove areas were converted to percent reflectance using four 8×8 metre reflectance tarps (4%, 16%, 32% and 48%) and empirical line calibration. These data were then compared to percent reflectance values of other terrestrial features to determine the ability of AISA+ data to distinguish features in coastal environments. Results suggest that these data may be appropriate to discriminate coastal mangrove vegetation and provide researchers with high resolution spatial and spectral information to more effectively manage coastal ecosystems.

Brain transcriptome sequencing and assembly of three songbird model systems for the study of social behavior

Emberizid sparrows (emberizidae) have played a prominent role in the study of avian vocal communication and social behavior. We present here brain transcriptomes for three emberizid model systems, song sparrow Melospiza melodia, white-throated sparrow Zonotrichia albicollis, and Gambel’s white-crowned sparrow Zonotrichia leucophrys gambelii. Each of the assemblies covered fully or in part, over 89% of the previously annotated protein coding genes in the zebra finch Taeniopygia guttata, with 16,846, 15,805, and 16,646 unique BLAST hits in song, white-throated and white-crowned sparrows, respectively. As in previous studies, we find tissue of origin (auditory forebrain versus hypothalamus and whole brain) as an important determinant of overall expression profile. We also demonstrate the successful isolation of RNA and RNA-sequencing from post-mortem samples from building strikes and suggest that such an approach could be useful when traditional sampling opportunities are limited. These transcriptomes will be an important resource for the study of social behavior in birds and for data driven annotation of forthcoming whole genome sequences for these and other bird species.

HOMING BEHAVIOR OF THE PUERTO RICAN FROG, ELEUTHERODACTYLUS COQUI

SMITH, M. A. 1943. The Fauna of British India, Ceylon and Burma, including the Whole of the IndoChinese Sub-region. Reptilia and Amphibia. Vol. III.-Serpentes. Taylor and Francis, London. UNDERWOOD, G. 1967. A Contribution to the Classification of Snakes. British Museum (Natural History), London. WALLACH, V. 1991. Comparative visceral topography of African colubrid snakes of the subfamilies Aparallactinae and Atractaspidinae. Unpubl. Masters Thesis, Louisiana State University, Baton Rouge. WILLIAMS, K. L. AND V. WALLACH. 1989. Snakes of the World. Vol. I. Synopsis of Snake Generic Names. Robert E. Krieger, Malabar. WONG, K. 1994. Visceral topography of the three genera of blind snakes of the family Typhlopidae (Reptilia: Serpentes). Unpubl. Masters Thesis, Northeastern University, Boston.

Variation in Preen Oil Composition Pertaining to Season, Sex, and Genotype in the Polymorphic White-Throated Sparrow

Evidence for the the ability of birds to detect olfactory signals is now well documented, yet it remains unclear whether birds secrete chemicals that can be used as social cues. A potential source of chemical cues in birds is the secretion from the uropygial gland, or preen gland, which is thought to waterproof, maintain, and protect feathers from ectoparasites. However, it is possible that preen oil also may be used for individual recognition, mate choice, and signalling social/sexual status. If preen oil secretions can be used as socio-olfactory signals, we should be able to identify the volatile components that could make the secretions more detectable, determine the seasonality of these secretions, and determine whether olfactory signals differ among relevant social groups. We examined the seasonal differences in volatile compounds of the preen oil of captive white-throated sparrows, Zonotrichia albicollis. This species is polymorphic and has genetically determined morphs that occur in both sexes. Mating is almost exclusively disassortative with respect to morph, suggesting strong mate choice. By sampling the preen oil from captive birds in breeding and non-breeding conditions, we identified candidate chemical signals that varied according to season, sex, morph, and species. Linear alcohols with a 10–18 carbon chains, as well as methyl ketones and carboxylic acids, were the most abundant volatile compounds. Both the variety and abundances of some of these compounds were different between the sexes and morphs, with one morph secreting more volatile compounds in the non-breeding season than the other. In addition, 12 compounds were seasonally elevated in amount, and were secreted in high amounts in males. Finally, we found that preen oil signatures tended to be species-specific, with white-throated sparrows differing from the closely related Junco in the abundances and/or prevalence of at least three compounds. Our data suggest roles for preen oil secretions and avian olfaction in both non-social as well as social interactions.

Quantitative color variation within and across morphs of the polymorphic White-throated Sparrow

ABSTRACT Coloration has evolved to serve diverse functions, including communication. In species with discrete color polymorphisms, the extent to which color variation exists within morphs and communicates multiple messages often remains unclear. We employed reflectance spectrometry to study variation in coloration in the dimorphic White-throated Sparrow (Zonotrichia albicollis), which exhibits a “white” and “tan” morph in both sexes. We explored whether distinct color traits distinguish between morph and sex classes, and whether color variation exists within classes that might reflect differences in individual quality. Further, we asked whether sexual dichromatism is more pronounced in the white morph, in which males display greater promiscuity and aggression and, thus, may be under stronger sexual selection for conspicuous coloration. Distinct aspects of crown plumage coloration differentiated the two morphs versus the two sexes and multiple types of coloration were associated with a morph, suggesting both multiple and redundant messaging functions of coloration. The brightness of white coloration and yellow carotenoid-based coloration differentiated the morphs, whereas the brightness and saturation of brown to black melanin-based pigmentation differentiated the sexes within morphs. However, coloration also varied considerably within morph and sex classes, potentially reflecting differences in individual quality. Finally, more sexual dichromatism existed within white morph than within tan morph birds. White morph males and females differed in white and yellow coloration, which also differentiated the morphs, and in melanin-based coloration. By contrast, tan morph males and females differed only marginally in coloration, and only in terms of melanin-based coloration. Results suggest that crown coloration is a multifaceted signal, and that selection has acted differently on coloration in both the morphs and the sexes. Our study suggests that multifaceted coloration can play multiple and redundant messaging functions, shows that color variation in polymorphic species can communicate more than morph, and suggests that morph-specific reproductive strategies alter selection on coloration.

Deer-Vehicle Collisions Along the Suburban-Urban Fringe

Deer-Vehicle Collisions (DVCs) are a significant problem in many areas of the United States (Conover et al. 1995). In 2002 alone, there were over 1.5 million DVCs resulting in over 1 billion dollars in damages, 150 human fatalities, and approximately 1.5 million white-tailed deer deaths (Curtis and Hedlund 2005). In sum, there are roughly 4,100 accidents/day resulting in over 2.7 million dollars of damage/day. DVCs are an increasing hazard to motorists as human development spreads into rural areas where residents commute daily to urban locations. Furthermore, through urban sprawl cities further encroach into environments where wildlife have no choice but to interact with humans. In many cases these interactions can have negative impacts for both humans and wildlife.

Genetic Verification of Dizygotic Twin Embryos in the White-throated Sparrow (Zonotrichia albicollis)

ABSTRACT The incidence of twinning in avian species is a phenomenon that has been rarely encountered. A number of domestic species have been shown to produce twins but in very low numbers. In wild populations, only 14 species have been documented producing twin embryos or nestlings. Despite this, it has been postulated that birds are just as likely as any other vertebrate to produce twin offspring. Here we describe the discovery of dizygotic twins in a long-term study of breeding ecology in the White-throated Sparrow (Zonotrichia albicollis). The twin containing egg was 12% heavier than the mean and had a mass greater than 94% of eggs collected. The twin containing egg was wider and longer than the majority of other eggs collected during 2010 but still within the expected range for White-throated Sparrows. Genetic analysis demonstrated that the twin embryos were full siblings but of different morph and sex. This is the first documented case of twinning in our study site out of over 2000 samples over 25 years of study, and likely the first confirmed case of twinning in this species.

Morph-Specific Patterns Of Reproductive Senescence: Connections To Discrete Reproductive Strategies

How reproductive strategies contribute to patterns of senescence in natural populations remains contentious. We studied reproductive senescence in the dimorphic white-throated sparrow, an excellent species for exploring this issue. Within both sexes the morphs use distinct reproductive strategies, and disassortative pairing by morph results in pair types with distinct parental systems. White morph birds are more colorful and aggressive than tan counterparts, and white males compete for extrapair matings, whereas tan males are more parental. Tan males and white females share parental care equally, whereas white males provide little parental support to tan females. We found morph-specific patterns of reproductive senescence in both sexes. White males exhibited greater reproductive senescence than tan males. This result likely reflects the difficulty of sustaining a highly competitive reproductive strategy as aging progresses rather than high physiological costs of competitiveness, since white males were also long-lived. Moreover, morph was not consistently related to reproductive senescence across the sexes, arguing against especially high costs of the traits associated with white morph identity. Rather, tan females exhibited earlier reproductive senescence than white females and were short-lived, perhaps reflecting the challenges of unsupported motherhood. Results underscore the importance of social dynamics in determining patterns of reproductive senescence.

Negative-Assortative Mating in the White-Throated Sparrow

Nonrandom mating based on phenotype has been observed in a number of organisms, but a very high proportion of these examples are of assortative mating. The strongest example of negative-assortative mating is for white-striped versus tan-striped crown in the white-throated sparrow, where about 98% of the observed pairings (mated pairs or social pairs) are between mates with different phenotypes and the correlation between mating types is -0.964. Although nonrandom mating has been explored theoretically for decades, these models have generally not focused on specific well-documented examples. Here we have developed a model to investigate the dynamics and equilibrium of this iconic example. The observed pattern of mating appears to be the result of 96% negative-assortative mating and a 17% advantage of W (white) male × T (tan) female matings compared to the reciprocal T male × W female matings. The equilibrium heterozygosity given these values is 0.500, very close to the 0.501 observed in our large sample of pairings, and this heterozygosity has been maintained for the 29 years from 1988 to 2016. In addition, the equilibrium frequency of 2m inversion determining the white-striped phenotype has been maintained at a frequency very close to its equilibrium frequency of 0.25. Overall, this model demonstrates how evolutionary genetic models can be used to understand negative-assortative mating.