The letter from Portman (1) regarding our PNAS article about the biparental bee (2) is an excellent contextual addition to male behavior in bees because the male role in hymenopteran societies is generally overlooked (3) and discussion about it can improve scientific awareness.
Portman (1) creates a summarization of examples of male presence in nests. Although the cited articles are very interesting, most of them are anecdotal observations based on a few observed individuals and without any rigorous samples that would allow statistical analysis. Therefore, it is impossible to conclude with certainty that biparental care is present in the species studied in the original studies. In most of the original papers that Portman (1) cites, different types of male association with nests were observed, and no author referred to the observed behavior as biparental care.
The study on Lasioglossum erythrurum (Cockerell) by Kukuk and Schwarz (4) reported a harem system, in which the macrocephalic male controls access to multiple females by nest guarding. Moreover, their paper reported male guarding in the late phase of nesting season when only pupae, adult females, and one guarding male are present in nests. Therefore, male guarding increases survival of pupae in nests, but these pupae can be siblings and not daughters of a guarding male. Male presence in nests of Lasioglossum zephyrum (Smith) and Augochlora pura (Say) reported by Barrows (5) seems to be accidental male visits of nests, not a regular male presence in nests.
The observation case of Ceratina smaragdula (Fabricius) male behavior was not connected to parental care. Males were observed to guard nests with adult offspring, not nests with currently provisioned brood cells (6). We agree that the most likely motivation for males is mate guarding; however, this is not connected to parental care. A male’s behavior can help him obtain more fitness but probably has no effect on protection of other individuals because mature offspring are able to protect themselves.
From the publications that Portman (1) mentions, the most promising species in which biparental care can occur is the colletid bee Leioproctus muelleri Houston and Maynard. Males of this species were observed to guard nests by more than 1 d during the phase of nesting season when females collected pollen (7). However, further research of this species is necessary to test whether the male helps with offspring protection and whether males obtain direct fitness benefits due to nest guarding.
We present a case of biparental care in bees in which the benefits for males and females are documented and a large sample size is used (2). It is likely that biparental care occurs in other bee species; however, extensive research of natural history and testing the relatedness between family members are necessary for understanding whether the species is truly biparental. We hope that the discussion supports interest in possible male nest behavior in bees and that more complex studies will be performed.
Footnotes
The authors declare no conflict of interest.
References
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