ASIAN MYRMECOLOGY Volume 10, e010009, 2018 ISSN 1985-1944 | eISSN: 2462-2362 © Aiki Yamada, Fuminori Ito, Rosli Hashim DOI: 10.20362/am.010009 and Katsuyuki Eguchi Queen polymorphism in Acanthomyrmex careoscrobis Moffett, 1986 in Peninsular Malaysia (Hymenoptera: Formicidae: Myrmicinae), with descriptions of hitherto unknown female castes and males Aiki Yamada1*, Fuminori Ito2, Rosli Hashim3 and Katsuyuki Eguchi1 1Systematic Zoology Laboratory, Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami- Osawa, Hachioji-shi, Tokyo, 192-0397, Japan. 2Laboratory of Entomology, Faculty of Agriculture, Kagawa University, Ikenobe, Miki 761-0795, Japan. 3Institute of Biological Sciences, University of Malaya, 50603 Kuala Lumpur, Malaysia. *Corresponding author: [email protected] ABSTRACT. The present study presents biological observations on colony characteristics of Acanthomyrmex careoscrobis Moffett, 1986 in Ulu Gombak (Selangor, Malaysia), with redescription of the minor worker and descriptions of the hitherto unknown female castes and males. The colony of A. careoscrobis can produce both alate and ergatoid queens. Ergatoid queens may function as cheap secondary reproductive females, whereas it is at present unclear whether they engage in dependent colony foundation or not. Ergatoid queens have the same number of ovarioles as alate queens, and show variable intermediate external morphology between major workers and alate queens. The colony redistributes nutrients via trophic eggs among colony members. Reviewing current available data for other Acanthomyrmex species, this study highlights the great prevalence and diversity of ergatoid queens in this poorly-studied genus. Keywords: ant, ergatoid queen, polyphenism, phenotypic plasticity, trophic egg. INTRODUCTION polymorphism or complete loss of alate queens and replacement by the wingless reproductives In most ant species, the queen possesses the full (Peeters & Molet 2010; Peeters 2012). However, complement of flight sclerites and muscles, and our knowledge of such females is still incomplete deciduous wings, i.e., the ability to fly while because the reproductives and life histories of the she has wings (hereafter this normal queen majority of ant species remain undescribed, and type is referred to as an alate/dealate queen). also because different types of queens may be In contrast, permanently wingless reproductive rare or conditionally expressed. females (ergatoid queen, brachypterous queen, The myrmicine ant genus Acanthomyrmex and gamergates) evolved independently in more Emery, 1893 is primarily restricted to the Oriental than 50 genera belonging to 16 ant subfamilies, realm, with one exceptional species A. notabilis with the result of either winged/wingless queen (Smith F., 1860) which is distributed on both 2 Aiki Yamada, Fuminori Ito, Rosli Hashim & Katsuyuki Eguchi sides of the Weber’s Line (Holt et al. 2013; at Van Ban (Lao Cai) had a single or multiple Janicki et al. 2016; Antmaps.org), consisting ergatoid queens. Both queen types were found in of 17 valid extant species (Bolton 2018); 11 separate colonies at Tay Yen Tu Nature Reserve species were recognized in a taxonomic revision (Bac Giang), though intracolonial polymorphism by Moffett (1986), and since six new species (i.e., production of both queen types in a single have been described (Terayama 1995; Terayama colony) has so far not been documented in this et al. 1998; Zhou & Zheng 1997; Eguchi et al. species (Eguchi et al., 2008). 2008). Colonies of this genus are commonly Moffett (1986) mentioned remarkable small (usually with less than 100 workers), and “variations” of the minor of A. basispinosus nests are found in cavities in dead twigs or rotten Moffett, 1986 and A. mindanao Moffett, 1986. wood, under or between stones and in litter on the These “variations” are likely misrecognition of forest floor. The nests of Acanthomyrmex species ergatoid queens, because the abnormal “minor” usually contain tiny seeds; A. ferox Emery, 1893 individuals show morphological traits similar exclusively gathers fig seeds from bird feces (Ito et to those of ergatoid queens in A. humilis, A. al. 2017), but colonies of A. glabfemoralis Zhou & padanensis, A. minus and A. sulawesiensis Zheng, 1997 often contain several undetermined (Yamada et al. unpublished). According to kinds of seeds (Yamada et al. unpublished). our morphological examinations of specimens Acanthomyrmex workers have ovaries but lack obtained through colony sampling (Yamada et al. spermatheca, and exhibit a distinct dimorphism, unpublished), A. concavus Moffett, 1986 and A. i.e., major workers (hereafter referred to as dusun Wheeler, 1919 also have ergatoid queens majors) and minor workers (minors) that are instead of alate queens (images of an ergatoid morphologically different. Majors are considered A. concavus queen given at AntWeb: https:// to serve in colony defense, seed milling and food www.antweb.org/specimen/CASENT0101061), storage (Moffett 1985; Buschinger & Maschwitz while A. crassispinus Wheeler, 1930 in Taiwan 1998; Terayama et al. 1998; Gobin & Ito 2000, exclusively had ergatoid queens, with similar 2003; Eguchi et al. 2008). All female castes were morphological traits to those of A. glabfemoralis shown to lay trophic eggs in A. ferox Emery, in Vietnam. These observations suggest that 1893 and nutrient redistribution via trophic eggs reproduction by ergatoid queens is more among colony members was confirmed (Gobin & prevalent in the genus Acanthomyrmex than Ito 2000). previously recognized. Queens in the genus Acanthomyrmex In the present paper, another case of have so far been described for seven species: queen polymorphism in this genus is reported. two species (A. ferox Emery, 1893 and A. Buschinger & Maschwitz (1998) mentioned an thailandensis Terayama, 1995) are characterized undetermined species found in Ulu Gombak, by the presence of alate queens, four species Selangor, Peninsular Malaysia, with notes on (A. humilis Eguchi et al., 2008, A. padanensis the habitat and role of the majors. With colonies Terayama et al., 1998, A. minus Terayama et al., newly collected in 1988 – 2013 by F. Ito in Ulu 1998, and A. sulawesiensis Terayama et al., 1998) Gombak, we confirmed that the undetermined are characterized by the complete replacement of species interestingly exhibits intracolonial queen alate queens with ergatoid queens (see Moffett polymorphism. The specimens were identified as 1986 and the original descriptions); and a single A. careoscrobis Moffett, 1986 which is previously species (A. glabfemoralis) exhibits intraspecific known only from the holotype minor collected from polymorphism of queen phenotype (Eguchi Gunung Mulu National Park (Sarawak, Malaysia), et al. 2008). Eguchi et al. (2008) reported that however future collection and examination of queenright colonies of A. glabfemoralis at four colony series from the type locality is necessary to sites in northern Vietnam (Chua Yen Tu (Quang confirm the taxonomic identity. Ninh Province), Ky Thuong Nature Reserve Here we present biological observations (Quang Ninh), Cuc Phuong National Park on the colony composition, new queen production, (Ninh Binh) and Pu Mat National Park (Nghe and egg-laying behavior of A. careoscrobis An)) had a single dealate queen, whereas those in Ulu Gombak. In addition, DNA barcodes, Queen polymorphism in Acanthomyrmex careoscrobis Moffett, 1986 in Peninsular Malaysia 3 redescription of the minor, and descriptions of the After rearing observations, several other female castes and the males are also given adult females from each colony were dissected. in the appendix for future comparison. Finally, a detailed morphological examinations of all castes and DNA barcoding were conducted. The voucher specimens are deposited in the MATERIALS AND METHODS following collections: AKYC, ACEG, and ACFI Ant collection of A. Yamada, K. Eguchi Caste terminology and F. Ito, respectively (see the contact address In the present paper, we use the term “ergatoid of the corresponding author); FRIM, Forest queen” to refer to permanently wingless Research Institute Malaysia, Kepong, Selangor, reproductive females that differ morphologically Malaysia; MCZC, Museum of Comparative from workers, following Peeters (2012). Zoology, Cambridge, Massachusetts, USA; MHNG, Muséum d’Histoire Naturelle, Geneva, Colony sampling and biological observation Switzerland. A total of nine Acanthomyrmex colonies were collected from a lowland rainforest near the Morphological examination and imaging Ulu Gombak Field Station of the University of Point-mounted specimens of the adult individuals Malaya in Selangor, Peninsular Malaysia, in July were examined with a Nikon SMZ1270 1998, August 1999, August – September 2009, stereomicroscope. Male genitalia were cleaned March 2011, and March 2013. Each colony was by Chelex-TE protocol (for details see Satria et given a unique colony code such as “FI98-77”. al. 2015), and then dehydrated in 99% ethanol, As many individuals as possible were collected dissected into several main components in a small alive from each colony. Adult members of each amount of Euparal on a slide glass, and covered caste were counted for each colony, and some with a cover slip. The morphological terminology adult females were dissected by F. Ito soon after follows Boudinot (2013). These slide-mounted collection in order to observe ovariole numbers specimens were examined with a Nikon Eclipse and the presence/absence of spermathecae. E600