Social behavior and kinship in the four-toed salamander, Hemidactylium scutatum

Berkey, Abigail Joy Maley

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Description

Title

Social behavior and kinship in the four-toed salamander, Hemidactylium scutatum

Author(s)

Berkey, Abigail Joy Maley

Issue Date

2015-04-23

Director of Research (if dissertation) or Advisor (if thesis)

• Phillips, Christopher A.
• Douglas, Marlis R

Doctoral Committee Chair(s)

Suarez, Andrew V.

Committee Member(s)

• Schooley, Robert L.
• Brawn, Jeffrey D.

Department of Study

School of Integrative Biology

Discipline

Ecol, Evol, Conservation Biol

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• population genetics
• dispersal
• gene flow
• differentiation
• Hemidactylium scutatum
• salamander
• amphibian
• behavior
• social behavior
• Kinship
• relatedness
• kin recognition
• kin discrimination
• aggression
• intraspecific
• distribution
• phenotype
• genotype
• phenotypic diversity
• geographic variation
• fluctuating asymmetry

Abstract

Amphibians are among the taxa experiencing the largest global decline in biodiversity. Many salamanders, especially North American members of the family Plethodontidae, are at risk of local extirpation because they persist in small, isolated populations due to specialized habitat requirements and limited dispersal ability. To effectively conserve and manage such species, factors influencing population connectivity and dynamics, such as dispersal and behavior, must be understood across various spatial scales. The Four-Toed Salamander, Hemidactylium scutatum, a species of concern in eastern North America, is a small-bodied plethodontid with a biphasic life cycle. Despite its broad geographic range, its occurrence is patchy due to specific breeding habitat requirements. Little is known about how distance between these habitat patches affects gene flow and which physical and biotic landscape features may act as barriers to dispersal. The population structure, i.e. gene flow and genetic diversity, of other plethodontid species is characterized by high levels of genetic divergence over relatively short distances and often reflects an isolation by distance pattern. In this study, I examined dispersal and population structure in H. scutatum from a local to a regional scale, focusing on the interaction between relatedness and dispersal (kin discrimination) and the potential for phenotypic traits to be used as a mechanism for kin recognition. I combined empirical observations with lab experiments to (1) examine population structure in H. scutatum (Chapter 1), (2) determine if phenotypic similarity between individuals is associated with genotypic similarity (Chapter 2), and (3) examine if kin discrimination is exhibited and potentially triggered by scent (Chapter 3). In Chapter 1, I used microsatellites to estimate genetic variation and gene flow within and among populations, calculate effective population size, and evaluate the possibility of population bottlenecks on both local and regional scales. The genetic data recorded a pattern of isolation-by-distance, characteristic of plethodontid salamanders. However, H. scutatum showed low genetic divergence among neighboring sites (1,000-2,000m). Several explanation exist for the low genetic divergence among populations including greater gene flow in H. scutatum compared to other plethodontids, relatively recent range expansion following the last Pleistocene glaciation, and a reduction in allele loss as a result of reduced whole clutch mortality in an indirect developing species. In Chapter 2 I examined the geographic and genotypic variation in the ventral spot pattern of H. scutatum. Specifically, if variation in color pattern is genetically controlled, color pattern may be used as a mechanism for kin recognition between conspecifics or be utilized in conservation decisions as an indicator of genetic diversity within a population. Additionally, I investigated the potential use of phenotypic traits as an indicator of stress or genetic diversity within populations. Fluctuating asymmetry, differences in the bilateral symmetry of a character due to disturbances in internal or external environments, influences color pattern in many in amphibian taxa and has the potential to be used as an indicator of at-risk populations under stress. Hemidactylium scutatum is characterized by a white ventral surface patterned with distinctive black spots. I used quantitative image analysis and microsatellite markers to investigate the potential influence of geographic variation on spot pattern and the potential relationship of phenotypic and genetic similarity. I also examined the possible influence of body condition, via fluctuating asymmetry, on spot pattern. While spot pattern exhibited significant variation on the regional scale, no relationship was found between spot pattern similarity and degree of kinship between individuals, suggesting that spot pattern is not used as a mechanism for kin recognition in H. scutatum. I also found no relationship between spot pattern symmetry and body condition. Combined, these findings suggest that, while spot pattern may not be useful for assessing genetic variation or population stress, it may be useful for taxonomists and allow recent immigrants to populations to be identified. In Chapter 3, I examined if isolated populations have increased degrees of kinship among individuals, potentially resulting in selection for kin recognition and kin discriminatory behaviors. Understanding the role of kinship in social behavior of at risk species such as H. scutatum may help in conservation and management efforts, especially those focusing on reintroduction and captive propagation programs. I investigated if there was an association between relatedness and aggressive behavior in H. scutatum by conducting behavioral trials in the lab and examined if related individuals may be spatially aggregated within a wild population. No relationship was found between the straight line distance between individuals and their relatedness. I also did not find a relationship between relatedness and aggressive behavior in the lab. It is possible that kin discriminatory behaviors differ between demographic groups or kin discrimination does not occur under the conditions observed in this study. Finally, the indirect development of H. scutatum may impact juvenile dispersal, resulting in a decreased rate of encounters between kin and decreased selection for kin recognition compared to other, direct developing plethodontid species.   ACKNOWLEDGEMENTS

Graduation Semester

2015-5

Type of Resource

text

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Copyright 2015 Abigail J. M. Berkey

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