Sociobiology 64(3): 244-255 (September, 2017) DOI: 10.13102/Sociobiology.V64i3.1623
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Sociobiology 64(3): 244-255 (September, 2017) DOI: 10.13102/sociobiology.v64i3.1623 Sociobiology An international journal on social insects RESEARCH ARTICLE - ANTS Natural History of Ants: What We (do not) Know about Trophic and Temporal Niches of Neotropical Species FB Rosumek Ecological Networks, Technical University of Darmstadt, Darmstadt, Germany Department of Ecology and Zoology, Federal University of Santa Catarina, Brazil Article History Abstract Our understanding of the natural history of Neotropical ants is limited, due to lack Edited by of descriptive efforts and widespread use of morphospecies in literature. Use Ricardo R. C. Solar, UFMG, Brazil Received 30 March 2017 of trophic resources and period of activity are two central niche aspects little Initial acceptance 24 May 2017 explored for most species. This work aimed to broadly review the literature and Final acceptance 05 June 2017 provide empirical field data on these aspects for 23 species. The fieldwork was Publication date 17 october 2017 carried out in the Atlantic forest of southern Brazil. Trophic and temporal niches were assessed with pitfall traps and seven kinds of bait representing natural Keywords Formicidae, Atlantic forest, Pheidole, resources. Crushed insects were the preferred resource, whereas bird feces Wasmannia auropunctata, Pachycondyla and living prey were less exploited. Most species broadly used the resources, striata, Odontomachus chelifer. but pronounced quantitative differences were found. Odontomachus chelifer (Latreille, 1802) and Pachycondyla striata Smith, 1858 were relatively well Corresponding author studied and field data matched previous accounts. They were the only species Félix Baumgarten Rosumek that consistently used large prey, and avoided oligosaccharides. Wasmannia Ecological Networks Technical University of Darmstadt auropunctata (Roger, 1863) differed remarkably from previous studies, using Schnittspahnstr 3, 64287 feces as its sole trophic resource. The six Pheidole species had no previous Darmstadt, Germany. records and presented quantitative differences in resource use. Most species E-Mail: [email protected] had no strong preference for period of activity.Camponotus zenon Forel, 1912 was nocturnal and Crematogaster nigropilosa Mayr, 1870, Linepithema iniquum (Mayr, 1870) and Linepithema pulex Wild, 2007 were diurnal. Complementary methods, context-dependence and descriptive studies have a central role in the understanding of ant natural history. Community assessments can contribute significantly to this knowledge if researchers also pay attention to the individual species involved. Introduction uncertainty, lack of descriptive studies and widespread use of morphospecies in literature (Krell, 2004; Greene, 2005). Ants (Hymenoptera: Formicidae) are among the most Two fundamental aspects that remain elusive for many abundant groups of invertebrates in terrestrial ecosystems, tropical species are trophic and temporal niche. Ants in general presenting a wide variety of feeding habits, nesting sites, and are regarded as omnivorous, feeding on a combination of interactions with organisms from all trophic levels (Kaspari, live prey, dead animals, seeds and plant exudates, with some 2000). They are the subject of extensive and diversified notorious specialized behaviors such as fungus cultivation and research, in basic and applied science. Despite this, in all pollen consumption (Kaspari, 2000; Blüthgen & Feldhaar, tropical regions, the biology of most species is virtually 2010). At genus or species level, they are sometimes classified unknown, due to a combination of high richness, taxonomic in broad groups or guilds like “generalist predators” or simply Open access journal: http://periodicos.uefs.br/ojs/index.php/sociobiology ISSN: 0361-6525 Sociobiology 64(3): 244-255 (September, 2017) 245 “generalists” (Brandão et al., 2012). These generalizations 30 to 50 m between plots. Distance between sample points have an important role to understand communities, but also was 10 m. The baits were set up in transparent plastic boxes leave out the remarkable variation among species in nature. with diameter of 10 cm and ground-level slits that allowed This specific information can be assessed from indirect sources the entrance of ants, and retrieved after 90 minutes. All such as body ratios of stable isotopes (Blüthgen et al., 2003) and individuals were collected from the baits in laboratory and remains found in nests (Lattke, 1990), and direct observation stored in ethanol 70% for subsequent sorting. such as interaction with plant resources (Byk & Del-Claro, Seven baits were offered as proxies for common resources 2010) and items carried to nests (Medeiros & Oliveira, 2009; available to ants (Table 1; see Supplementary Material for Raimundo et al., 2009). Every approach has its focus and details on bait display and rationale for their choice). In each limitations, and adds a piece to the puzzle that is the niche of round, only one bait was offered per sample point, and bait a species. types were mixed among points, with a similar number of In turn, studies on temporal niche of ants are common points receiving each type (8-9 per round). Fourteen baiting in open areas and/or temperate habitats, where the fluctuations rounds were performed, with only one period sampled each in abiotic factors could have a stronger effect on ant activity. day, at daytime (around 13:00-15:30) or nighttime (around This variation is often linked with temporal niche partitioning 21:00 – 23:30). In total, 896 baits were applied in the 64 sample and coexistence of competing species (Lessard et al., 2009; points, with all seven baits being offered in each sample point Anjos et al., 2016). Less information is available for tropical two times (one at day and one at night). This design is suitable forests (e.g. Medeiros & Oliveira, 2009; Raimundo et al., to assess multidimensional trophic niches, which are inferred 2009; Feitosa et al., 2016). Inside a forest, less variation would from how often ants use each resource. Hence, “preferences” be expected, because daily changes in temperature, humidity means simply relative high use of certain resources. Distance and wind are smaller. However, temporal niche could still be between each colony and the bait does not change from one affected by the existing fluctuations or by competitive pressure. resource to another, and the use of one resource does not affect In view of the importance of both use of trophic the other. Thus, it differs from a typical cafeteria experiment, resources and period of activity, and considering the lack which is designed to assess preferences through choices among of information available for most Neotropical species, this different resources offered at the same time (Krebs, 1999). work aims to quantify use of trophic resources and period of An independent community assessment was performed activity of ground-dwelling ants from a Neotropical forest. with three rounds of pitfall trapping, alternated with bait An extensive literature review was performed to assess how rounds. The plastic cups were 6 cm wide and contained much is known about these individual species and compare propylene glycol 50% and a small amount of neutral detergent. results from the viewpoint of complementarity of methods and Cups were buried previously and replaced after each round ecological context-dependence. These case studies highlight to avoid the digging-in effect. Pitfalls stayed opened for 10 that descriptive studies are still fundamental for tropical hours during the day and 9 hours during the night (due to faunas. In this sense, broader ecological assessments can give short summer nights), then an extra 3-hour nocturnal round a significant contribution, if researchers also pay attention to was performed. One nocturnal and one diurnal pitfall round the individual species involved. were performed in sequence, separated by intervals to avoid dusk and dawn times. Methods Specimen processing and identification Study area and sample design For each sample point, at least one individual per Fieldwork was carried out in Desterro Conservation morphospecies was mounted. They were identified to genus Unit, Florianópolis, south Brazil (27o31’38’’ S, 48o30’15’’ level with Baccaro et al. (2015) and to species level with W, altitude ca. 250 m), between December 2015 and January taxonomic revisions, and comparison to identified specimens 2016. Average annual temperature and precipitation is 20.5 in collections and Antweb images (AntWeb, 2016). The ºC and 140 mm per month (data from meteorological station of taxonomic sources used were: Crematogaster – Longino EPAGRI/CIRAM). Vegetation consists of secondary Atlantic (2003); Cyphomyrmex – Kempf (1965) and Snealling and forest sensu stricto (= ombrophilous dense forest) with at Longino (1992); Gnamptogenys – Lattke (1995); Hylomyrma least 60 years of relatively undisturbed regeneration. This – Kempf (1973); Linepithema – Wild (2007); Odontomachus work was conducted in accordance with Brazilian laws, under and Pachycondyla – Fernández (2008); Pheidole – Wilson authorization SISBIO number 51173-1. (2003); Wasmannia – Longino and Fernández (2007). The sampling was based on the recent design of Camponotus and Strumigenys were identified just by Houadria et al. (2015) to assess community patterns on comparison with collections. The identifications were resource use and daily activity, but here its suitability to partially confirmed by taxonomists of the Laboratory of understand