Ecology and nesting biology of the woodboring bee

Authors: Nydia Vitale Diego P Vázquez

Publish Date: 2016/05/02

Volume: 48, Issue: 1, Pages: 31-40

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Abstract

Studying bee nests can enlighten our understanding of feeding specialization and phylogenetic relationships of bees We studied the nesting and feeding habits of Trichothurgus laticeps in the Monte desert ecosystem Our results show that T laticeps is attracted to preexisting cavities in wood trap nests which were further excavated for nest construction nest cells are unlined and provisioned almost exclusively with pollen of the cactus Opuntia sulphurea The species overwinters inside a hard cocoon Our results reinforce the hypothesis previously proposed by other authors that the unworked pollen mass and oligolecty are plesiomorphic characters in the Megachilidae and that the woodboring behavior for nest construction indicates convergent evolution with the Xylocopinae We also propose that the cocoon structure might represent an evolutionary novelty for the LithurginaeThe study of bee nests including their architecture the structure of brood cells the type of provisions and larval behavior may enhance our understanding of the ecology and evolution of bees Michener 2007 The Megachilidae is an imposing bee family with over 4000 described species Ascher and J Pickering 2010 Phylogenetic studies suggest this family is monophyletic Danforth et al 2013 Hedtke et al 2013 Litman et al 2011 RoigAlsina et al 1993 with four subfamilies Fideliinae Lithurginae Pararhophitinae and Megachilinae Danforth et al 2013 Hedtke et al 2013 It is accepted that Fideliinae is the sister clade to the remainder of the family Danforth et al 2013 Hedtke et al 2013 Litman et al 2011 Michener 2007 While morphological studies Gonzalez et al 2012 indicate that the Pararhophitinae are more basal than the Lithurginae molecular studies are less conclusive given that both groups exhibit several plesiomorphic characters Hedtke et al 2013 Litman et al 2011Studying bee nests can also illuminate our understanding of feeding specialization in bees Although a number of bee species have been identified as purported pollen specialists eg Neff 2003 Neff and Simpson 1992 in many cases this conjecture rests primarily on visitation observations or scopal pollen loads which usually represent a single foraging trip Sipes and Tepedino 2005 In contrast pollen provisions in bee nests offer copious information on the foraging habits of female bees integrating their resource use in space and time Several studies have so far attempted to evaluate pollen specialization in bees using pollen provisions in brood cells Bosch et al 1993 Buschini et al 2009 Dórea et al 2013 Gonçalves et al 2012 Rust et al 2004 Schlindwein et al 2009The available information on nesting and feeding habits is extremely limited for some groups in the Megachilidae which hinders our understanding of their phylogenetic relationships This is the case for the Lithurginae for which the information on nesting habits is particularly limited This subfamily includes four genera Lithurgus Lithurgopsis Microthurge and Trichothurgus There is information about the nesting biology of the former three genera from several studies with at least 12 studies on Lithurgus and Lithurgopsis species Rozen 2013 Rozen and Hall 2014 one study on one Microthurge species M corumbae Garófalo et al 1992 and additional notes on the occurrence of other species in South America Ascher and J Pickering 2010 Moure and Melo 2012 Most species in these three genera excavate their burrows in wood and construct their nests with unlined brood cells Rozen 2013 trophically they range from oligolectic feeding on few plant species Díaz and Cocucci 2003 to polylectic feeding on many plant species of multiple families Güler and Sorkun 2007 The information available for Trichothurgus is comparatively rather limited coming from anecdotal nesting observations of T dubius ClaudeJoseph 1926 Rozen 1973 and a study of T bolithophilus in which this species was observed nesting in dry horse dung Sarzetti et al 2012 Although Trichothurgus species were believed to feed primarily on pollen from cactus Michener 2007 T bolithophilus was recorded feeding primarily on pollen from the Asteraceae and Amaranthaceae Sarzetti et al 2012 Thus it is unclear whether the anecdotic records of the nest building and provisioning habits of T dubius and T bolithophilus are representative of the diversity of nesting habits of Trichothurgus and whether the above observations indicate a departure from the wood nesting habits of Lithurgus and Microthurge Answering these questions should improve our understanding of the evolution of the nesting habits of lithurgine bees and of the phylogenetic relationships within this group and with other bee groups

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