Spatial Heterogeneity and Clonal Structure in Arctic Populations of Apomictic Daphnia
1989
Weider, Lawrence J.
Allozymic surveys of obligately parthenogenetic Daphnia pulex from a Canadian high—arctic island revealed high levels of clonal richness in these populations. The present study was conducted to elucidate the underlying spatial patterns of clonal distributions. Three—way G tests of independence indicated significant within—pond spatial and temporal heterogeneity of clones. In addition, spatial autocorrelation analysis indicated significant between—pond patterning of clones,although distributions were patchy. Generally, clones found at low frequencies in a given pond showed restricted distributions, while the most abundant clones were widespread across the island. Principal components analysis revealed that certain clones were distributed differentially in ponds, which varied in size, relative age, and location on the island. The present clonal composition on the island is most likely the result of multiple colonization events during the period of deglaciation. Between—pond clonal distributions are influenced strongly by the probability of passive dispersal of resting eggs (ephippia) via any number of dispersal vectors (e.g., avian, human). Elucidation of the underlying mechanisms that maintain clonal diversity and influence clonal distributions in this Daphnia assemblage requires further study of both deterministic (e.g., selection) and stochastic (i.e., historical) factors.
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