![]() ![]() Therefore, it is important to compare the efficiency of the various techniques for sampling ant diversity in one place to advance knowledge about ant fauna in hyper-diverse regions, especially in the litter ( Castilho et al., 2007 Veiga-Ferreira et al., 2010 Hanisch et al., 2018). Ant community researchers suggest combining different techniques as the best way to estimate ant richness and abundance ( Delabie et al., 2000a Longino et al., 2002 Gotelli et al., 2011). No method can collect all the species that inhabit a specific area because these species usually have a great diversity of foraging and nesting habits ( Pacheco & Vasconcelos, 2012 Salata et al., 2020). Several methodologies have been used to collect ants from the soil, each of which has limitations. Because of these characteristics, ants have frequently been used as a focal taxon in biodiversity studies or as bioindicators in soil management studies ( Schimidt & Solar, 2010 Pacheco & Vasconcelos, 2012). In addition, they contribute in an extraordinary way to the edaphic processes, such as the movement of water and soil and the cycling of nutrients ( Sousa-Souto et al., 2007). They play critical ecological roles, acting as herbivores, seed dispersers, or predators of other arthropods and scavengers ( Del Toro et al., 2012 Andersen, 2019). Ants are a hyperdiverse group in tropical forests and particularly important in the soil macrofauna, as they are highly abundant, have a wide geographical distribution, and occupy a wide variety of niches ( Andersen & Majer, 2004 Solar et al., 2016 Tiede et al., 2017). However, it is challenging to estimate species richness in megadiverse regions because the techniques used by researchers do not always provide a representative sample of total richness ( Agosti & Alonso, 2001 Orsolon-Souza et al., 2011 Tista & Fiedler, 2011). ![]() This is noteworthy as if we manage to locally eradicate YCA in the future, the absence of a competitor may make way for another ant species to invade Vallée de Mai, or indeed allow native ants to return.Studies of soil macrofauna require well-structured and standardized sampling methodologies to adequately estimate species richness and uniformity ( Véle et al., 2009). ![]() Populations of other invasive alien ants such as Technomyrmex albipes, Nylanderia bourbonica and Odontomachus simillimus have also decreased substantially since baiting started in 2019. The high numbers of YCA in Fond Peper are also of major conservation concern given the site’s importance for endemic caecilians, geckos, skinks, black parrots, snails, slugs and many other invertebrates. It also highlights the potential for rapid reinvasion if control efforts are not sustained. The Fond Peper survey shows us how abundant YCA could have been had no action been taken to arrest their increasing population. The substantial decrease of YCA in the Vallée de Mai strongly suggests that the two fipronil treatments this year were highly effective in reducing YCA numbers and bolsters our confidence in further reducing them with another baiting deployment in March. ![]() On the other hand, the results showed the highest numbers of YCA in Fond Peper since pitfall surveys began. YCA appear to have returned to the distribution from 2010 they are found in highest abundance only in the north-east of the forest. The results showed that YCA now occupy 60% of the Vallée de Mai in very low numbers (0–9 individuals) which is the smallest distribution since 2015 and the lowest numbers since they were first discovered in the site. The resulting 75 samples (50 from the Vallée de Mai and 25 from Fond Peper) were then sorted in December. Another survey was carried out in Fond Peper without AntOff treatment for comparison. The YCA taskforce used a more ergonomic pitfall trap design for this survey in the Vallée de Mai, which was treated with AntOff (the ant bait). In December we surveyed the numbers of ants using pitfall traps, to assess the impact of baiting on YCA distribution and abundance. The Seychelles Islands Foundation (SIF) responded to this threat by setting up a dedicated YCA taskforce earlier last year, who have carried out two rounds of baiting in the forest in an attempt to reduce the numbers of YCA. The yellow crazy ant (YCA) is an invasive alien species and causes significant impacts on the native wildlife of the Vallée de Mai. Environment YCA surveys in the Vallée de Mai suggest that baiting has reduced numbers of ants |02 March 2020 ![]()
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