Sexual selection, reproductive strategies, and genetic variation in the longear sunfish (Lepomis megalotis)
Jennings, Martin J.
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Permalink
https://hdl.handle.net/2142/19792
Description
Title
Sexual selection, reproductive strategies, and genetic variation in the longear sunfish (Lepomis megalotis)
Author(s)
Jennings, Martin J.
Issue Date
1991
Doctoral Committee Chair(s)
Philipp, David P.
Department of Study
Biology
Discipline
Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Ecology
Biology, Genetics
Agriculture, Fisheries and Aquaculture
Language
eng
Abstract
Starch gel electrophoresis was used to examine genetic variability among longear sunfish Lepomis megalotis. Principal component analysis of allele frequency data could not separate the most morphologically distinct form, L. m. peltastes, from L. m. megalotis. Southwestern populations, for which the names L. m. breviceps and L. m. aquilensis are available, clustered as distinct groups. L. marginatus was genetically most similar to the southwestern forms.
Nesting habitat was quantified and offspring mortality from biotic versus abiotic sources was compared within a naturally occurring population of central longear sunfish. Excess suitable nesting habitat was available. Nesting activity could be limited by flow regime, which varied stochastically. Destruction of nests by flooding was an important source of brood mortality, accounting for as much brood loss as all biotic factors combined.
Mating systems with spatial clumping of nests can result from female preferences for clumping or from competitive interactions among males. I tested predictions derived from these two types of models in central longear sunfish. The data were consistent with models for male-initiated spatial clumping. Large males had greater mating success than small males and solitarily nesting males were larger than colonial males; the most successful males were solitary nesters. Male mating success did not increase with colony size. Successful colonial males were often cuckolded by neighbors, whereas solitary males were not cuckolded. Colonial nesting is maintained and may have evolved in longear sunfish because group nesting allows subordinate males to obtain access to fertilizations.
The cost of reproduction is central concept of life history theory. Relationships between physiological reproductive investment and somatic growth were evaluated within and among populations of longear sunfish. Within populations, tactical allocation of energy to reproductive functions in precociously mature males is associated with reduced somatic growth rates. Subspecies that vary in adult body size were grown in experimental ponds; somatic growth was reduced in the population with greater reproductive investment. Among local populations of L. m. megalotis gonadal investment differed but growth rates became different only after maturity; these results confirm that there is a growth cost to reproduction; phenotypic variation is at least partly the result of differences in lifetime reproductive strategies.
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