BIOTYPE, GENOMOTYPE, AND GENOTYPE - VARIABLE EFFECTS OF POLYPLOIDY AND HYBRIDITY ON ECOLOGICAL PARTITIONING IN A BISEXUAL-UNISEXUAL COMMUNITY OF SALAMANDERS
La. Lowcock, BIOTYPE, GENOMOTYPE, AND GENOTYPE - VARIABLE EFFECTS OF POLYPLOIDY AND HYBRIDITY ON ECOLOGICAL PARTITIONING IN A BISEXUAL-UNISEXUAL COMMUNITY OF SALAMANDERS, Canadian journal of zoology, 72(1), 1994, pp. 104-117
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.