Using genetics to understand BehaviorJeanette McGuirePhD CandidateDepartment of ZoologyMichigan State UniversityBehavioral ObservationsPhoto: Jen SmithAre you my Dad?Or brother?Are we related at ALL?What about species that are difficult to observe?• Nocturnal• “Skittish”• Mating takes place out of view (underwater)Ways to use genetics as a tool•Migration– Movements– Geneflow• Life history– Age of reproduction– Males!•Mating– Assortative mating?– Direct fitness– Inclusive fitness– Identification of individuals• Identify relationshipsAn example: My dissertation research• Mating systems of freshwater turtlesThe problem:Despite many researchers studying turtles, very little is actually known about the mating systems of turtles. As in many species, we know (comparatively) a lot about females, but not much about males. The problem:We cannot observe matings. So how do we find out:At what age do males start/stop reproducing?Who is mating with whom?Quantify reproductive successFor both Males and Females RS = the number of offspring + quality of offspringHowever, the way reproductive success (RS) is attained is different RS of females is primarily constrained by resources: egg size, egg number, potentially number and quality of matesRS of males is primarily constrained by the number of females mated and the quality of those females Bateman 1948, Trivers 1972Multiple paternity and RSPotential benefits for females include increased genetic variability of offspring, increased probability of having offspring sired by a high quality male, and genetic complementaritiesPotential benefits for males include increased number of offspring sired.(The double-edged sword: Multiple paternity may increase or decrease an individuals reproductive success)Study SiteStudy Site: The University of Michigan’s Edwin S. George Reserve• Short tandem repeats• Mendelian inheritance pattern• Highly variableMicrosatellitesTail clip or BloodDNAPCRINSERT GEL IMAGE! 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 161 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16So what have we done so far?• We have examined multiple paternity in snapping turtles and painted turtles• Analyzed incidence of multiple paternity as a function of characteristics of the female.Snapping turtle: Chelydra serpentina• Long-lived (>55 years)• Delayed sexual maturity of females (11-17 yrs on ESGR)• Sexual size dimorphism with males larger than females• Females store sperm • Multiple paternity of clutches (Galbraith et al. 1992)• Sexual size dimorphism, forced insemination (?) and male-male combat combine to make an interesting mating system compared to many other species of turtlesSnapping Turtle Mating SystemFemale attributes related to RSAmong adults there is no correlation between body size and age• Larger females have larger clutches and slightly larger eggs than do smaller females• Older females do not have larger clutches, but have larger eggs than do younger femalesCongdon et al., 1987, Iverson, 1990, Congdon unpublished dataBecause older and larger females have increased RS, males of all phenotypes would benefit from mating with those femalesPredictions:P1: Larger and/or older females will have a higher incidence of multiple paternity than will smaller femalesP2: Larger and/or older females will have a lower incidence of multiple paternity than will smaller females (However, older but small females may be less able to fend off males)1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 161 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16Preliminary Results¾1999-2004 Overall incidence of multiple paternity 42% of 40 clutches¾Incidence of multiple paternity was highly variable among years¾2002: 20% (n=15)¾2003: 60% (n=15)¾2004: 50% (n=8)Sample sizes will increase when unobserved females can be genetically identified Generalized linear mixed effect model: Logistic Regression AnalysisDependent Variable: Paternity 0=single paternity1= multiple paternityIndependent Variables• Random effect: Year• Fixed effects– Clutch size (p=.032)*– Body size of female (carapace length) (NS, p=.33)– Age of female (NS, p=.07)Statistics preformed using “R”Percentage of Multiple Paternity with Age020406080100<20 20-25 26-35 35+Ages (years)Percentage of Multiple Paternity (%)N= 9N= 13N= 9N= 9Percentage of Multiple Paternity with Body Size020406080100<231 231-240 241-250 250+Body Size (Carapace Length, mm)Percentage of multiple paternity (%)N=8N=14N=10N=8Preliminary ConclusionsPredictions:P1: Larger and/or older females will have a higher incidence of multiple paternity than will smaller females• Combined analyses suggest the potential for a positive correlation between age and multiple paternityPreliminary ConclusionsPredictions:P2: Larger and/or older females will have a lower incidence of multiple paternity than will smaller females (However, older but small females may be less able to fend off males)• No significant relationship was observed between body size and incidence of multiple paternity. However, the slight positive relationship between multiple paternity and body size provides potential support for prediction 1. Ongoing Work• Adding data from 31 clutches from 2005, 23 clutches from 2006• Adding more clutches through genetic identification of unobserved females that produced nests • Total final sample size will be 127 nests• Adding more loci for genetic identification of individuals• Identification of the males siring clutches– Intensive trapping 2005-2007– Male phenotypesPainted turtle life history: ESGR• Long-lived (>54 years)• Delayed sexual maturity (females 7-13, males ?)• Adult sex ratio 2.3:1 (M:F)• Sexual size dimorphism (females larger)• Females store sperm• Multiple paternityCongdon et al. 2003 Painted turtles: Reproduction• Clutch frequency is highly variable:– Maximum of 2 clutches each year (Schwarzkopf and Brooks, 1985, Congdon et al., 2003) – some not every year (Tinkle et al. 1981)• Clutch size – average 7.6– range (2-13)Painted turtles: summary• Much is known– information about life history • Females• Female reproduction– Sex ratio– Population size– Long lived– Highly variable in qualityFemale Attributes related to RS• Clutch size increases with body size• Egg size increases with body size• Clutch frequency increases with ageBecause older and larger females