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Reproductive Isolation in Clearwing Moths (Lepidoptera: Sesiidae): A Tropical‐Temperate Comparison
Author(s) -
Greenfield Michael D.
Publication year - 1983
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1937082
Subject(s) - sex pheromone , reproductive isolation , ecology , biology , interspecific competition , pheromone , niche segregation , species richness , panama , lepidoptera genitalia , ecological niche , zoology , habitat , population , demography , sociology
To elucidate the factors promoting reproductive isolation in a diverse tropical community of clearwing moths (Lepidoptera: Sesiidae), I compared the results of pheromone trapping studies conducted in Panama with previously published studies involving Wisconsin Sesiidae. Pair—forming behavior in sesiids is facilitated by female—emitted sex pheromones which serve as long—range attractants for conspecific males. Pheromones of the various species appear to be closely related in terms of chemical structure. Prior work in Wisconsin demonstrated that species maintain reproductive isolation through specificity in sex pheromone chemistry and differences in seasonal or daily pattern of sexual activity. In both Wisconsin and Panama, data were obtained by trapping male sesiids with synthetic pheromone baits. An objective comparison of reproductive isolation in the two regions is accomplished through an application of metrics (breadth, overlap) developed originally to measure niche segregation. The atmospheric channel along with sex communication occurs is considered as an entity, and the chemical and temporal axes along which the communication channels of species may differ are viewed as dimensions. Interspecific differences in channels along a dimension constitute a reproductive isolating mechanism. The calculations of channel breadths and overlaps along these dimensions permit a quantitative comparison of isolating mechanisms. Theory predicts that in species—rich communities either breadths are narrower, overlap greater, or channel availability (space) is more extensive along one or more dimensions. Species richness of sesiids was significantly greater in Panama on both a regional and a local basis. Seasonal breadths of sesiids were greater in Panama than in Wisconsin. However, when seasonal breadths were standardized to account for the extended favorable season in Panama, values in both regions were equivalent. Chemical breadths of species that apparently utilized mixtures of different compounds as sex pheromones (binary species) were comparable in Panama and Wisconsin, as were overlaps along the seasonal and chemical dimensions. However, a higher proportion of the Panamaian fauna were binary isomer species, and Panamanian sesiids appeared to utilize a greater diversity of compound mixtures as pheromones. This indication that greater channel space distinguishes two communities differing is species richness agrees with several recent findings, regarding niche segregation, in other taxa.