Biodiversity of leaf litter and arboreal ants (Hymenoptera: Formicidae) in a temperate Mid-Atlantic forest
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Bioindicator species, whose presence and/or abundance are likely to change with natural and man-made changes, can provide important information regarding the environmental health of a particular ecosystem. My research aimed to measure the diversity and species richness of leaf litter ants (Hymenoptera: Formicidae) in the E.A. Vaughn Wildlife Management Area (WMA), a temperate forest on the lower eastern shore of Maryland. Additionally, leaf litter depth and mass was investigated to determine if there was a relationship with ant abundance at this field site. Leaf litter was collected along twenty-four, 100m transects during May, July, and September of 2015 and placed into Berlese funnels for ant extraction. A total of 14 species were collected from 144 leaf litter samples. Estimates of species richness (Chao1: 14.0 species, ACE: 15.0 species) suggest there may be one additional species that was not sampled in my study; a species accumulation curve suggests similar findings. Diversity measures were relatively low with a Shannon exponential of 4.88 and Simpson reciprocal of 2.82. The leaf litter of E.A. Vaughn WMA was dominated by a single species, Nylanderia faisonensis (Forel 1922), which accounted for 57.3% of the total ant specimens collected. Neither leaf litter depth (R2= 4E-5) nor mass (R2= 9E-6) was found to have a substantial impact on ant abundance as a whole. When individual species were examined for relationships between ant abundance and leaf litter depth/mass, no significant values were found. Thus, we conclude that leaf litter does not predict ant abundance. Key Words: bioindicator, Berlese funnel, North temperate forest, diversity, species richness, Nylanderia faisonensis Environmental indicator taxa are sensitive to disturbance and can be used to indicate the health of a habitat. Indicator taxa provide an estimation of species variety, often in terms of the number of different species in a given area that can be monitored and used to gain an overview of changing ecosystem trends (Andersen 1997; McGeoch 1998; Longino et al. 2002). Indicator taxa can also be used to locate areas of high biodiversity (biodiversity indicators) or estimate the impact from a specific one time disturbance event (Caro and O’Doherty 1999). High levels of diversity in a given region act as a safeguard against the collapse of an ecosystem; the loss of a single species may be filled by another with a similar niche or by other organisms with similar lifestyles (Ribas et al. 2003). Biodiversity surveys rely on indicator taxa for conservation planning, developing management plans, studying the impact of agricultural practices on habitat, and providing justification for the existence of protected areas (Spector and Forsyth 1998; Caro and O’Doherty 1999). Ants are often cited as excellent bioindicator taxa due to their great numbers, species variety, and ability to occupy the vast majority of terrestrial habitats (Andersen 1997; Bestelmeyer and Wiens 2001; Martelli et al. 2004; Underwood and Fisher 2006) which in turn allows researchers to study a number of different aspects of ecosystems and the species that inhabit them (Andersen 1997; Steiner et al. 2005). Ant are also known to react quickly to changes in their habitat, with decreased diversity levels after an ecosystem is disturbed and increasing as the habitat recovers (Longino et al. 2002; Martelli et al. 2004; McGlynn et al. 2009). Leaf litter ants, in particular, are useful in predicting plant diversity (Resende et al. 2013). While ants are not the only family of insects that can be used as a bioindicators, their large biomass make large scale changes to their numbers easy to observe (Ivanov and Keiper 2009). Some authors suggest that minute changes may have an impact on populations utilizing microhabitats, thus the loss of ant species in a fragmented habitat could have a profound impact on the ecosystem as a whole (Crist 2009). The role of leaf litter mass in predicting ant abundance has been mixed, with some studies finding a correlation between increased amounts of leaf litter and ant abundance (Lopes and Vasconcelos 2008; McGlynn et al. 2009) while others found no support (Lynch et al. 1988; Wilkie et al. 2010) or only very weak support (Kaspari 1996a). Regardless of human interaction, approximately 60% of known ant species have been reported living in leaf litter, suggesting it is a critical habitat to examine (Silvestre et al. 2012). The majority of ant studies take place in the tropics despite their widespread distribution (Ellison et al. 2007), leading to a lack in ant diversity data elsewhere (Lynch 1981, Lynch et al. 1988). One reason for this may be due to the difficulty in the collection and curation of the vast numbers required to survey a field site (Wilkie et al. 2010). Another complication is that ant collection methodology is varied with no one methodology being ideal in all situations (Agosti et al. 2000; Ivanov and Keiper 2009; Lopes and Vasconcelos 2008). Commonly used methods to examine ant biodiversity are often time intensive, and require knowledge of the terrain type to efficiently collect data (Frye et al. 2014). Thus, finding the ideal collection method for a particular habitat type is of utmost importance when undertaking a study (Vele et al. 2009). Many studies however use multiple sampling methods because of the lack of consensus about the best way to sample ants (Agosti et al. 2000; King and Porter 2005). While disagreement regarding sampling techniques is common, there is agreement that more research needs to be performed, especially outside of the tropics. Within many regions of the United States, basic information such as species range is incomplete, even for common ant species. Partial state inventories have been conducted in Florida (King and Porter 2005), Oklahoma (Albrecht and Gotelli 2001), Tennessee (Sanders et al. 2007b), New York (Ellison et al. 2007), Oregon (Ratchford et al. 2005; Sanders et al 2007a) and California (Ratchford et al. 2005; Sanders et al 2007a). The only state to have completed what is considered a full inventory of all ants in its borders is Ohio (Coovert 2005; Ellison et al. 2007). In Maryland ant studies and investigation of ant ecology, have mostly focused on species richness and seasonality in habitats west of the Chesapeake Bay (Lynch et al. 1980, Lynch 1981, Lynch et al. 1988) or interactions between different ant species (Fellers 1987, Fellers 1989). On Maryland’s Eastern Shore, only two biodiversity studies have been conducted. Frye and Frye (2012) hand collected ants from trees in the ridge woodlands and inland sand dune communities of Worcester County, MD. Thirty-five species of ants were sampled from 241 trees. Frye et al. (2014) on the other hand, used pitfall traps and leaf litter samples to examine ant species richness and diversity. They reported 67 species of ants from 25 genera. Both of these studies, however, were restricted to xeric habitats characterized by dry conditions with low moisture levels (Frye et al. 2014). The objective of my research was to determine the ant species diversity and richness of leaf litter ants in the E.A. Vaughn Wildlife Management Area (WMA), a temperate forest in Worcester Co., Maryland. Additionally, leaf litter depth and dry leaf litter mass were measured to determine if there was a correlation with ant abundance. Seasonality was not a primary focus of this study though some natural history data is provided.