Moderate Fire Severity Is Best for the Diversity of Most of the Pollinator Guilds in Mediterranean Pine Forests
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Ecology, 100(3), 2019, e02615 © 2019 by the Ecological Society of America Moderate fire severity is best for the diversity of most of the pollinator guilds in Mediterranean pine forests 1,2 1 1 2 MARIA LAZARINA, JELLE DEVALEZ, LAZAROS NEOKOSMIDIS, STEFANOS P. S GARDELIS, 2 1 1 1 ATHANASIOS S. KALLIMANIS, THOMAS TSCHEULIN, PANAGIOTIS TSALKATIS, MARINA KOURTIDOU, 1 1 3 3 4 VANGELIS MIZERAKIS, GEORGIOS NAKAS, PALAIOLOGOS PALAIOLOGOU, KONSTANTINOS KALABOKIDIS, ANTE VUJIC, 1,5 AND THEODORA PETANIDOU 1Laboratory of Biogeography & Ecology, Department of Geography, University of the Aegean, Mytilene 81100 Greece 2Department of Ecology, School of Biology, Aristotle University, Thessaloniki 54124 Greece 3Department of Geography, University of the Aegean, Mytilene 8110 Greece 4Department of Biology and Ecology, University of Novi Sad, Trg Dositeja Obradovica 2, 21000 Novi Sad Serbia Citation: Lazarina, M., J. Devalez, L. Neokosmidis, S. P. Sgardelis, A. S. Kallimanis, T. Tscheulin, P. Tsalkatis, M. Kourtidou, V.Mizerakis, G. Nakas, P. Palaiologou, K. Kalabokidis, A. Vujic, and T. Petanidou. 2019. Moderate fire severity is best for the diversity of most of the pollinator guilds in Mediterranean pine forests. Ecology 100(3):e02615. 10.1002/ecy.2615 Abstract. Fire, a frequent disturbance in the Mediterranean, affects pollinator communi- ties. We explored the response of major pollinator guilds to fire severity, across a fire-severity gradient at different spatial scales. We show that the abundance of all pollinator groups responded to fire severity, and that bees and beetles showed in addition a significant species- diversity response. Bees, sawflies, and wasps responded to fire severity at relatively small spatial scales (250–300 m), whereas flies and beetles responded at larger spatial scales. The response of bees, sawflies, and wasps was unimodal, as predicted by the intermediate disturbance hypothesis, whereas flies and beetles showed a negative response. A possible explanation is that the observed patterns (spatial scale and type of response) are driven by taxa-specific ecological and life-history traits, such as nesting preference and body size, as well as the availability of resources in the postfire landscape. Our observational study provides an insight into the effect of fire severity on pollinators. However, future research exploring the explicit link between the pre- and postfire landscape structure and pollinator traits and responses is required for further establishment and understanding of cause–effect relationships. Key words: abundance; bee flies; bees; beetles; diversity; fire severity; generalized additive models; hoverflies; intermediate disturbance hypothesis; sawflies; wasps. INTRODUCTION definitions of fire severity are built around the fire- induced environmental change. Fire-severity metrics, Fire is an important disturbance acting worldwide as a quantifying the impact of fire intensity on plant biomass ’ key ecological process, shaping organisms distribution loss or decomposition, have been shown to be associated and determining ecosystem dynamics, structure, and func- with ecosystem responses to fire (Keeley et al. 2011). tioning (Bond et al. 2005). The effects of fire on ecosys- Remote-sensing approaches constitute an alternative for tems and biota depend on the physical characteristics of the quantification of fire severity, and have gained interest fire, such as fuel consumption and fire spread patterns, recently (Key and Benson 2006, Kolden et al. 2015). fire intensity and severity, frequency, burnt patch size and In the Mediterranean, a spatially and environmentally distribution, and seasonality (Bond and Keeley 2005, heterogeneous region characterized by its climate, wild- Pausas and Keeley 2009, Keeley et al. 2011). Fire inten- fire is a frequent disturbance playing a major role in sity, defined as the energy release during different phases shaping natural ecosystems (Pausas et al. 2009). Such of fire (Keeley et al. 2011), is considered a critical fire fires frequently result in a mosaic of regenerating postfire characteristic that affects species and ecological communi- community complexes in the Mediterranean Basin (Elia ties (Parr and Andersen 2006, Pastro et al. 2011). How- et al. 2012), and this landscape diversification has a ever, as fire intensity is difficult to measure, fire severity is major effect on plant and insect communities. Fire affects often used instead as a proxy (Keeley et al. 2011). General pollinator communities, directly through mortality from heat, smoke, and destruction of nests, and indirectly by Manuscript received 22 June 2018; revised 29 October 2018; accepted 3 December 2018. Corresponding Editor: Gordon A. driving changes in vegetation and soil (Moretti et al. Fox. 2006). Viewing the pollinator response to fire in a time 5 Corresponding Author. E-mail: [email protected] perspective, an initial decrease in pollinator abundance Article e02615; page 1 Article e02615; page 2 MARIA LAZARINA ET AL. Ecology, Vol. 100, No. 3 and diversity shortly after fire is followed by a peak the of response variables (species richness, diversity, and abun- first two to three postfire years, followed by a gradual dance), across a spatial gradient of different fire-severity decline over the following years (Ne’eman et al. 2000, levels. We performed our analysis for all pollinator groups Potts et al. 2003, Moretti et al. 2006). Therefore, an at different taxonomic levels to detect family- and species- extension of the intermediate disturbance hypothesis specific responses, as species-rich families include species (Grime 1973, Connell 1978) seems to apply. This hypoth- with diverse traits. We explore two key features of the pol- esis predicts a unimodal diversity and disturbance rela- linator response: (1) spatial scale and (2) type. To address tionship, with the highest diversity observed at spatial scale, we assume that traits such as insect body intermediate levels (frequency or intensity) of distur- size, trophic specialization, nesting and foraging require- bance, assuming a trade-off between species’ ability to ments, as well as flight range, are important determinants compete and to tolerate disturbance. of the spatial-scale response of different taxa (Jauker et al. There has been a considerable amount of research on 2009, Tscheulin et al. 2011, Neokosmidis et al. 2018). taxonomical and functional responses of pollinators to Regarding the type of response, we hypothesize the exis- fire across different time scales (e.g., Petanidou and Ellis tence of a taxon-specific fire-severity threshold, beyond 1996, Moretti et al. 2006, 2009, Campbell et al. 2007, which diversity, richness, and abundance decrease. We Grundel et al. 2010, Williams et al. 2010, Cruz-Sanchez emphasize that this is an observational study and the et al. 2014). However, relatively little is known about the pollinator response to fire severity was evaluated using spatial scale and the type of response of pollinator com- postfire data. Because it is based on a natural experiment, munities to fire severity. Fire affects landscape structure it was not possible to know the prefire patterns in pollina- over a wide range of spatial scales, changing soil proper- tor diversity and abundance. Therefore, our study assists ties, vegetation structure, and postfire availability and in understanding the way species respond to fire severity, spatial distribution of nesting and floral resources (Mor- but cannot be regarded as a definitive demonstration of etti et al. 2006). Different insect taxa perceive and cause–effect relationships. exploit the environment at different spatial scales, depending on their traits and requirements (Steffan- MATERIAL AND METHODS Dewenter et al. 2002, Holland et al. 2005, Petchey and Gaston 2006, Jauker et al. 2009), and even ecologically Study system and site selection and morphologically similar species may respond at dif- ferent scales (Redhead et al. 2016). However, regarding The major part of the study area lies within the pollinator response to fire severity, our knowledge Dadia–Lefkimi–Soufli Forest National Park (41°070– derives more indirectly from their response pattern over 41°150 N, 26°190–26°360 E), which is part of the Dadia– time (e.g., Petanidou and Ellis 1996, Ne’eman et al. Lefkimi–Soufli forest complex, located at Lefkimi, 2000, Potts et al. 2003, Moretti et al. 2006, 2009, Camp- Thrace, NE Greece (Fig. 1A). The area is a complex of bell et al. 2007, Grundel et al. 2010, Williams et al. pine (Pinus brutia and P. nigra) and oak (Quercus frai- 2010, Cruz-Sanchez et al. 2014), or through studies netto, Q. cerris, and Q. pubescens) forests, also including investigating responses to other disturbances, such as other habitat types and landscape features such as culti- grazing and habitat loss (Lazaro et al. 2016a, b,Kovacs- vations, pastures, torrents, and stony hills. The climate is Hostyanszki et al. 2017), than directly (but see Thom sub-Mediterranean, with dry summers and relatively et al. 2015, Ponisio et al. 2016). These studies discuss cold winters (mean annual rainfall ca. 650 mm, mean the intermediate disturbance hypothesis. For example, annual temperature 14.3°C; Maris and Vasileiou 2010). Lazaro et al. (2016a, b), using data from Mediterranean This study examines the effects of a wildfire event that plant–pollinator communities, found that an intermedi- occurred on 24 August 2011, lasted 4 d, and burnt 5,900 ate grazing intensity promotes pollinator diversity. Other hectares of pine