BIOTYPE, GENOMOTYPE, AND GENOTYPE - VARIABLE EFFECTS OF POLYPLOIDY AND HYBRIDITY ON ECOLOGICAL PARTITIONING IN A BISEXUAL-UNISEXUAL COMMUNITY OF SALAMANDERS

It is hypothesized that coexistence of bisexual and unisexual salamand ers depends upon various forms of ecological partitioning, as in analo gous complexes of fishes. The mixture of clonal and nonclonal, obligat ely sperm-dependent reproduction occurring in unisexual mole salamande rs of the genus Ambystoma suggests that some of this partitioning may be manifest in the variable reproductive attributes of different bioty pes and in community structure. Within biotypes, ecological difference s related to genomic composition (genomotype) and specific origin (gen otype) of individuals are also expected. Using data gathered over a 4- year period from a large population of the A. laterale-jeffersonianum complex from Haliburton, Ontario, I examined four areas of reproductiv e ecology that may contribute to ecological partitioning: (1) fluctuat ing sex, hybrid, and ploidy ratios; (2) differential migratory respons e by triploid and tetraploid genomotypes; (3) ontogenetic differences among triploid and tetraploid genomotypes; and (4) genotypic differenc es within unisexual genomotypes. For each case I was able to reject a null hypothesis ascribing ecological equivalency to those biotypes inv olved. The most germane ecological differences among unisexuals were i mbedded in the broad syndrome of delays in larval development, metamor phosis, and sexual maturity displayed by tetraploids. These findings p arallel those reported in a large body of literature generated from la boratory studies of polyploid salamanders. Using these corresponding d ata, I conducted a broad review of potential developmental, physiologi cal, and biotypic causes and consequences of the observed delays. The results indicated that several effects of polyploidy and hybridity dir ectly influence community ecology and contribute to stable coexistence of bisexuals and unisexuals. Based on these findings, a strategic mod el summarizing interaction in these communities was constructed, from which testable hypotheses may be derived for future research. The find ings of this study confirmed the ontological status of the biotypic di stinctions (genomotype versus genotype) advanced here.