Paixão, Ferreira & Paixão

Spatial distribution and seasonal behavior of Endecous aguassay and Eidmanacris lencionii (: Grylloidea: ) in an artificial iron ore cave

Emanuelle Arantes Paixão1,2, Rodrigo Lopes Ferreira1,3 & Crysttian Arantes Paixão4

1 Center of Studies in Subterranean Biology, Biology Department, Federal University of Lavras, 3037 University Campus, Lavras, Minas Gerais, 37200-000, Brazil 2 [email protected] 3 [email protected] (corresponding author) 4 Center of Rural Sciences, Curitibanos Campus, Federal University of Santa Catarina, 101 Rodovia Ulysses Gaboardi Km 3, Curitibanos, Santa Catarina, 89520-000, Brazil [email protected]

Key Words: Endecous aguassay (Orthoptera: Grylloidea, Phalangopsidae), Eidmanacris lencionii (Orthoptera: Grylloidea, Phalangopsidae), Nova Lima, Minas Gerais, Brazil, Spatial segregation.

Cricket species of the genus Endecous (Family Phalangopsidae) are widely distributed and highly abundant in Brazilian caves (Ferreira and Martins 1999), with occurrence records in many cavities (Souza-Dias et al. 2014). Souza-Dias et al. (2014) emphasized that this genus occurs in all Brazilian biomes and in subterranean environments, and among genera, it is the most conspicuous and widespread. According to Ferreira (2005), species of Endecous are troglophiles, specialized to the cave environment, and Souza-Dias et al. (2014) state that these crickets inhabit the entrance and the dark zones in caves. Eidmanacris (Family Phalangopsidae) also occurs in Brazilian caves (Pinto-da-Rocha 1995), but its occurrence in caves is still poorly known (Bolfarini 2016). This genus has straminicolous and cavicolous habits, and in the later, species of this genus use natural caves for refuge (Desutter-Grandcolas 1995). According to Souza-Dias et al. (2015), species of Eidmanacris inhabit the entrance and adjacent cavities.

In general, cave-inhabiting species in these two cricket genera can be classified as generalist detritivores feeding on guano and organic debris, such as leaves and rotting logs. Ferreira (2005) proposed a trophic network for Neotropical iron ore caves in which crickets in the family Phalangopsidae feed on guano. Additionally, Phalangopsidae have been directly recorded feeding on bat guano and on bat corpses or found on guano (Ferreira and Martins 1999). Souza-Dias et al. (2014) observed Endecous apterus Bolfarini & Souza-Dias, 2013 feeding on dead arthropods (Amblypygi and Trichodamon sp.) and Silva et al. (2012) found Endecous sp. feeding on a characiform carcass. These records indicate an opportunistic generalist diet.

In this study, we analyzed spatial variation of two sympatric cave crickets Endecous aguassay Mews, 2008 (Figure 1A) and Eidmanacris lencionii Bolfarini, 2016 (Figure 1B)

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inhabiting an artificial iron ore cave in Brazil (Nova Lima, Minas Gerais) in the Quadrilátero Ferrífero, one of the main Brazilian ferruginous geosystems. This artificial gallery is 30 meters of horizontal projection, with an average width and height of 1.5 and 1.8 meters respectively. Due to a sinuous passage occurring just after the entrance, most of the cavity remains in permanent and total darkness. The cave contains three primary regions where the two species were found: an outer region (first 8 meters from the entrance – a disphotic area), middle region (corresponding to 15 meters of the cave passage), and an inner region (deepest portion of the cave, last 7 meters) (Figure 2).

Figure 1. Cricket species in this study, A) Endecous aguassay and B) Eidmanacris lencionii, from an artificial iron ore cave in Nova Lima, Minas Gerais, Brazil. Scale bars correspond to 1 cm. Photographs by Rodrigo L. Ferreira.

The data used for our analysis came from eight monitoring trips conducted every three months from February 2005 to November 2006; sampling events took place in both rainy and dry seasons of the year. During each monitoring trip, the spatial location of each individual of E. aguassay and E. lencionii was recorded on a map of the cave. Visual surveys were conducted in pairs, with one person counting and recording the positions of individuals and the other person observing previously recorded individual to ensure that a cricket was not recorded more than once. As the cave is very narrow, we had access to all microhabitats for visual surveys. We did not identify individual crickets to life stage or gender. During each monitoring trip, the temperature and the humidity were measured on the wall in the middle part of the gallery with a Hygrotherm Center 130 hygrometer. Differences in temperature and humidity between the rainy and dry seasons were analyzed using Student's t-test and an α=0.05.

Spatial point pattern analysis (SPPA; Bailey and Gatrell 1995; Gatrell et al. 1996; Diggle 2013) was employed to analyze the spatial patterns of the two species and their relationships. The intensity estimates, i.e., the expected number of points per area unit, were performed by Isotropic Gaussian Kernel (Gatrell et al. 1996; Baddeley 2010). These estimates result in intensity maps that can be used to identify possible spatial distribution patterns independent (completely random), regular or clustered for each species in each monitoring period. Furthermore, these data can be used to identify the locations in the cave where individuals tend to cluster. These spatial observations were statistically

2017 Speleobiology Notes 9: 23–33 24 Paixão, Ferreira & Paixão confirmed by K function (Ripley 1977), with simulation envelopes by the Monte Carlo method with 50,000 simulations (Gatrell et al. 1996; Baddeley 2010). Ripley (1981) stated the significance level of 5,000 simulations is about 0.0004. The cross K function was used to evaluate the spatial relationship independence, repulsion or attraction between the two species also with simulation envelopes by the Monte Carlo method with 50,000 simulations (Gatrell et al. 1996; Baddeley 2010). All analyses were performed in R software (R Core Team 2016) using the Spatstat package (Baddeley and Turner 2005).

Since both species of crickets were using both the cave floor and walls, the figure representing the map of the cave was "adapted" to exhibit the current position of each individual observed. Hence, the final map is a bi-dimensional scheme of the current three- dimensional cave. For that purpose, the cave walls were "planned," thus their height was summed to the width of the cave conduit, producing the final figure. Since no cricket was observed in the cave ceiling, it was not represented in the final map. Accordingly, the cavity map used to illustrate the clustered regions for each species has 30 meters of horizontal projection and 5.1 meters of length (1.5 meters of the average width) added to the two walls (1.8 meters high of each wall) (Figure 2).

Figure 2. Layout of the artificial iron ore cave located in Nova Lima city, Minas Gerais state, Brazil, in Quadrilátero Ferrífero karst area. For data analysis, the cavity was divided into three regions: Outer (first 8 meters from the entrance), Middle (corresponding to 15 meters of the cave passage), and Inner (deepest portion of the cave, last 7 meters).

The average temperature recorded was 19.8°C (ranging from 18 to 21°C, SD=1.1) and the relative humidity was 87.5% (ranging from 76 to 95%, SD=7.0). The rainy and dry seasons did not differ statistically in relation to any temperature (average temperature of the rainy season was 20.4°C and the dry 19.2°C; t-stat=-1.79; d.f.=5.60; P=0.13) nor humidity (average humidity of the rainy season was 92% and the dry 83%; t-stat=2.35; d.f.=3.67; P=0.08). These results confirm the topoclimatic stability of the cavity.

We observed seasonal changes in spatial distribution of both cricket species within the cave passage, varying from rainy to dry season and differing between species (Table

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1, Figure 3). In monitoring conducted on 14 May 2005, the intensity maps of the E. aguassay (Figure 4A) and E. lencionii (Figure 4C) showed regions with a higher average density of points, i.e., clusters. The K function estimations confirm the clustered pattern for all analyzed distances between points (r) for E. lencionii (Figure 4D). However, for E. aguassay, two patterns were observed, random and clustered (Figure 4B). In most of the monitoring trips, the two species exhibited a clustered pattern at all r values except for E. aguassay on 27 February 2005 and 14 May 2005 (Figure 5A) and E. lencionii on 27 February 2005 (Figure 5B).

Regarding the interaction between the two species, the intensity maps revealed a seasonal pattern (Figure 3). In the rainy season, there is a tendency of a marked segregation between the two species, with populations of E. aguassay concentrated in the middle and innermost regions of the cave, while E. lencionii tends to inhabit areas near the cave entrance. During the dry season, E. lencionii tends to concentrate in the innermost region of the cavity. However, when the estimates of the K cross function are analyzed, the spatial pattern is not so evident (Figure 5C). For example, in the second monitoring trip, the two species showed independence and attraction patterns (Figure 4E and 5C). The observed spatial patterns (Table 1, Figures 3, 4 and 5) of E. aguassay and E. lencionii may be due to several factors, including but not limited to ecological interactions, differing microhabitat preferences, degree of cave adaptation, behavioral differences, or competition but it in fact there are distinct seasonal variations that differ between the two taxa.

As caves are oligotrophic environments (Culver 1982; Simon et al. 2007), the quantity and distribution of resources may be factors that contribute to the existence of the clustering pattern observed in both cricket species. Moreover, clustering may be a behavior against dehydration (Yoder et al. 2002).

Table 1. The number of individuals observed for the two cricket species, Endecous aguassay and Eidmanacris lencionii, for each region of the artificial iron ore cave (Inner, Middle, and Outer) during each of eight monitoring trips. N is the total number of specimens for each species on that date.

Monitoring Season Endecous aguassay Eidmanacris lencionii Period Inner Middle Outer N Inner Middle Outer N 27-Feb-05 Rainy 11 25 1 37 – – 16 16 14-May-05 Dry 19 27 3 49 15 – 34 49 21-Aug-05 Dry 45 43 – 88 40 4 14 58 19-Nov-05 Rainy 110 154 18 282 – – 5 5 18-Feb-06 Rainy 188 156 16 360 5 – 7 12 25-May-06 Dry 30 151 – 181 21 5 29 55 24-Aug-06 Dry 43 127 27 197 29 – 9 38 22-Nov-06 Rainy 109 171 22 302 – – 2 2

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Figure 3. Intensity maps for E. aguassay (END) and E. lencionii (EID) during each monitoring trip from 27 February 2005 to 22 November 2006 associated with rainy and dry seasons. The scale in each map represents the number of expected points per area unit.

Spatial overlap with segregation seasonally and by temperature has been documented for the syntopic Slovenian cave spiders Meta menardi (Latreille, 1804) and Metellina merianae (Scopoli, 1763) (Novak et al. 2010). Spatial segregation by age class has been observed in the cave salamander Hydromantes (Speleomantes) strinatii Aellen, 1958 in relation to differences in invertebrate abundance and temperature (Ficetola et al. 2013). In Europe, Sebastiano et al. (2012) found niche partitioning in two forest salamander species Speleomantes strinatii (Aellen, 1958) and Salamandrina perspicillata (Savi, 1821) occurred seasonally when prey biomass was reduced. Finally, for some cave inhabiting crickets, there is evidence of movement by time-of-day and days since last surface foraging excursion by crickets which forage on the surface (Campbell 1976; Taylor et al. 2005). Additionally, populations of cave crickets may differ from entrance to deep cave regions in relation to age classes due to their reproduction and forage functions (Lavoie et al. 2007).

The spatial data suggest that E. lencionii may be more tolerant to desiccation or less cave-adapted, because this species tends to remain closer to the cave entrance. Cave crickets often have a fast water loss rate (Yoder et al. 2002); stygius (Scudder, 1861) concentrate in cave entrances and are less cave-adapted and retain water more effectively than Hadenoecus cumberlandicus Hubbell & Norton, 1978. Hadenoecus cumberlandicus shows a preference for the deep cave regions, and adult females are aggregated to regulate water loss (Yoder et al. 2002).

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Figure 4. Spatial point pattern analysis of the two cricket species during the monitoring trip on 14 May 2005. Intensity maps are shown for E. aguassay (A) and E. lencionii (C). In (B) and (D), the estimations of K function are shown; r is the distance argument between points, the dashed line corresponds to the theoretical K function considering complete spatial randomness and solid line is the empirical K function based on observed data. The Monte Carlo method allows estimating the upper and lower curves, which delimit the envelope of the theoretical K function; the shaded region corresponds to the completely random pattern. In (E), K cross function estimations are presented considering the spatial interaction between the two species.

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(A)

(B)

(C)

Figure 5. Spatial distribution patterns of E. aguassay (A) and E. lencionii (B), based on estimates of the K function, according to the distance between points (r) for each monitoring trip associated with rainy and dry seasons. Spatial relationships, considering K cross function estimates, between the two species are shown in C. For some monitoring trips, it was not possible to estimate the K and K cross functions due to the low abundance of the species.

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Observed differences in distribution patterns for E. aguassay and E. lencionii in our study could be related to selection of suitable oviposition substrates. Pellegatti-Franco (1997) observed that Endecous itatibensis Rehn, 1918 exhibited greater reproductive success (percentage of outbreaks observed in each laying) than Strinatia brevipennis Chopard, 1970 when the two species were maintained at the same time under the same laboratory conditions. The authors suggested these differences may be related to differing oviposition strategies, with S. brevipennis being more selective in relation to oviposition substrate. In contrast, E. itatibensis oviposited quickly in any available substrate laying large numbers of eggs (average 21 eggs/female).

Pinto-da-Rocha (1995) stated Endecous species have a spatial distribution that is usually widespread within cave habitats, ranging from the entrance to deeper cave regions. Our results suggest E. aguassay distribution changes seasonally. Our study also revealed that E. aguassay tended to be found deeper within this cave than E. lencionii. Souza-Dias et al. (2014) reported that E. apterus were mainly concentrated in the dark zone of a cave located in the state of Bahia, Brazil. Moreover, Souza-Dias et al. (2015) reported a personal observation by Bolfarini & Souza-Dias on the presence of Eidmanacris individuals only in the cave entrance and individuals of Endecous in deep cave region.

Since the completion of this study, we visited the cave on two other occasions: on 22 October 2009 (dry season) and 06 February 2015 (rainy season). During these visits, we again recorded the position of each of the two cricket species. However, contrasting patterns to those observed during our study was observed: individuals of E. aguassay were concentrated in the outer region of the cave, besides being observed also in the middle region, during both subsequent monitoring trips, and individuals of E. lencionii were concentrated in the outer region on 22 October 2009 and in the inner region on 06 February 2015.

Given the contrasting patterns observed during our subsequent visits in 2009 and 2015, additional long-term studies are important in the future that encompass a greater number of rainy and dry cycles to support the general patterns observed during our original study. Although several factors were suggested here as possible explanations for the observed pattern, it is not possible to verify yet which are most important. We recommend that future studies examine microhabitat preference of E. aguassay and E. lencionii as well as competition tests that consider the different life stages and sex of each species. Furthermore, studies that measure the temperature and humidity of the cavity in a more detailed way, making measurements in the outer, middle and inner regions are important. Such studies will be able to correlate these temperature and humidity with external environmental conditions, providing a better understanding of the seasonal pattern.

Considering our lack of knowledge regarding the biology and ecology of cave organisms associated with iron ore caves, our data show intriguing patterns, which highlight the need of further studies to better understand ecological mechanisms to explain the observed temporal and spatial patterns. Such studies will provide a deeper

2017 Speleobiology Notes 9: 23–33 30 Paixão, Ferreira & Paixão understanding of the functioning of Brazilian iron ore cave ecosystems, thus facilitating more effective conservation and management alternatives for these unique subterranean ecosystems.

Acknowledgements

We thank CAPES (Coordination for higher Education Staff Development) for financial support, the staff at the Center of Studies in Subterranean Biology (UFLA) for helping with fieldwork, Steven J. Taylor, Matthew L. Niemiller, and the anonymous reviewers for their helpful and enriching comments. We are also grateful to Rodrigo Antônio Castro Souza for cricket identification. Rodrigo L. Ferreira is also thankful for CNPq (National Council of Technological and Scientific Development) for the research grant (Process No. 304682/2014-4). Literature Cited Baddeley, A. 2010. Analysing spatial point patterns in R. Workshop notes. CSIRO, Australia. http://research.csiro.au/software/wp- content/uploads/sites/6/2015/02/Rspatia Icourse CMIS PDF-Standard.pdf. Downloaded on 18 November 2015.

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