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Factors affecting female‐biased sex ratio in a trap‐nesting wasp, Trypoxylon malaisei
Author(s) -
Oku S.,
Nishida Takayoshi
Publication year - 1999
Publication title -
population ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 59
eISSN - 1438-390X
pISSN - 1438-3896
DOI - 10.1007/s101440050019
Subject(s) - sex ratio , biology , sex allocation , offspring , competition (biology) , nest (protein structural motif) , zoology , male to female , ecology , demography , medicine , genetics , population , pregnancy , biochemistry , sociology , retrospective cohort study
We examined the female‐biased sex ratio of a trap‐nesting wasp Trypoxylon malaisei considering the following factors: (1) local mate competition (LMC), (2) resource quality, (3) partial bivoltinism, and (4) presence of constrained females. The sex ratio (expressed as male ratio) at emergence was strongly female biased, i.e., 0.30 and 0.19, in terms of the number and investment, respectively. To evaluate the primary sex ratio, we analyzed the data from nests where all the offspring successfully emerged, excluding nests composed of single‐sex offspring. The primary sex ratio was also female biased, at 0.33 and 0.21, in terms of the number and investment, respectively. LMC was highly responsible for the female‐biased sex ratio because both the nonrandom oviposition sequence [females at inner cells and male(s) at outer cells] and earlier emergence of males allowed sib‐matings to occur. In contrast, the other three factors little affected the female‐biased sex ratio: the sex ratio was fairly constant when resource quality (nest size) varied, partial bivoltinism was extremely rare or absent, and constrained females were absent or did not reproduce at all.