Taxonomic Revision of the Obligate Plant-Ants of the Genus Crematogaster Lund (Hymenoptera, Formicidae, Myrmicinae), Associated with Macaranga Thouars (Euphorbiaceae) on Borneo and the Malay Peninsula

Abstract

The taxonomy and natural history of ants of the genus Crematogaster Lund, 1831 (Crematogaster borneensis-group of the former subgenus Decacrema) obligately associated with myrmecophytic host-plants of the euphorb genus Macaranga are reviewed. Within this group of ants Crematogaster borneensis André, 1896 (with five subspecies and four varieties), Crematogaster captiosa Forel, 1910 as well as Crematogaster decamera Forel, 1910 have previously been described from SE Asia. Here we synonymise C. borneensis subsp. capax Forel, 1911, C. borneensis subsp. hosei Forel, 1911, C. borneensis subsp. sembilana Forel, 1911, and C. borneensis var. macarangae Viehmeyer, 1916 with C. borneensis André, 1896. Crematogaster borneensis var. harpyia Forel, 1911, C. borneensis var. insulsa Forel, 1911, C. borneensis subsp. symbia Forel, 1911, and C. borneensis subsp. novem Forel, 1911 are synonymised with C. captiosa Forel, 1910. In addition we describe five new species: C. claudiae sp. nov., C. hullettii sp. nov., C. linsenmairi sp. nov., C. maryatii sp. nov., and C. roslihashimi sp. nov.. Seven of these eight species are placed into two informal species subgroups based on queen morphology, life-history characters and a formerly published molecular phylogeny. Keys are provided for the identification of queens and workers, as well as natural history information on the eight ant species. The morphology of these Macaranga-associated Crematogaster (formerly Decacrema) species is compared to the only other three species described for this former subgenus in SE Asia, i.e. C. angulosa André, 1896, C. biformis André, 1892 and C. cephalotes Smith, 1857.

Taxonomy of coccids (Hemiptera: Coccidae: Coccus L.) associated with Crematogaster ants (Hymenoptera: Formicidae) in the stems of Macaranga plants (Euphorbiaceae) in Southeast Asia

“…The codes for these ant lineages follow the nomenclature of Quek et al (2007). Note S1 in the supporting information of Quek et al (2017) attempts to reconcile these lineages with the ant species described in Feldhaar et al (2016). We have not attempted to list the names of the ant species associated with each of the coccid collections listed in this revision.…”

“…In a few cases identifications of the ants were not made and, for some collections with ants, these contain mostly worker ants that are difficult to identify to species. All of the ants collected in Brunei by PJG from M. trachyphylla were C. captiosa Forel, and all from M. beccariana were C. decamera Forel, based on identifications made by PJG based on queen morphology supplemented by worker ant characteristics as given in Feldhaar et al (2016).…”

“…Myrmecophytism involving varying degrees of plant morphological specialisation has evolved more than once within Macaranga but only in the western Malesian lineage of the genus, with myrmecophytic species found in three Macaranga sections, namely Pachystemon, Pruinosae and Winklerianae (Blattner et al 2001;Davies et al 2001;Bänfer et al 2004). The relationship is obligate for certain Crematogaster ants, which nest only inside these myrmecophtic Macaranga species Fiala & Maschwitz 1992a;Feldhaar et al 2016). The taxonomy and phylogeny of these specialist ants have been the subject of a number of studies (e.g.…”

“…Fiala et al 1999;Itino et al 2001;Feldhaar et al 2003;Quek et al 2007;Feldhaar et al 2010;Ueda et al 2015;Feldhaar et al 2016) and currently the majority of the ants are recognised as belonging to the Crematogaster borneensis-group (Blaimer 2012), comprising eight species (Feldhaar et al 2016). These ants colonise Macaranga hosts in the sections Pachystemon (naturally-hollowing stems) and Pruinosae (solid stems, excavated by ants), whereas plants in the section Winklerianae are colonised only by C. morphospecies 8 that belongs to a different Crematogaster subclade (Feldhaar et al 2016). The natural history of these ants, including data on the Macaranga species inhabited by each ant species, was reviewed by Feldhaar et al (2016).…”

“…These ants colonise Macaranga hosts in the sections Pachystemon (naturally-hollowing stems) and Pruinosae (solid stems, excavated by ants), whereas plants in the section Winklerianae are colonised only by C. morphospecies 8 that belongs to a different Crematogaster subclade (Feldhaar et al 2016). The natural history of these ants, including data on the Macaranga species inhabited by each ant species, was reviewed by Feldhaar et al (2016).…”