Canopy cover negatively affects arboreal ant species richness in a tropical open habitat

Abstract

We tested the hypothesis of a negative relationship between vegetation characteristics and ant species richness in a Brazilian open vegetation habitat, called candeial. We set up arboreal pitfalls to sample arboreal ants and measured the following environmental variables, which were used as surrogate of environmental heterogeneity: tree richness, tree density, tree height, circumference at the base of the plants, and canopy cover. Only canopy cover had a negative effect on the arboreal ant species richness. Vegetation characteristics and plant species composition are probably homogeneous in candeial, which explains the lack of relationship between other environmental variables and ant richness. Open vegetation habitats harbor a large number of opportunistic and generalist species, besides specialist ants from habitats with high temperatures. An increase in canopy cover decreases sunlight incidence and may cause local microclimatic differences, which negatively affect the species richness of specialist ants from open areas. Canopy cover regulates the richness of arboreal ants in open areas, since only few ant species are able to colonize sites with dense vegetation; most species are present in sites with high temperature and luminosity. Within open vegetation habitats the relationship between vegetation characteristics and species richness seems to be the opposite from closed vegetation areas, like forests.Keywords: environmental heterogeneity, microclimate, vegetation characteristics, hierarchical partitioning, candeia.A cobertura de dossel afeta negativamente a riqueza de formigas arborícolas em um hábitat tropical aberto ResumoNós testamos a hipótese de que há uma relação negativa entre as características da vegetação e a riqueza de espécies de formigas em habitats abertos como o candeial. Para isto, nós instalamos pitfalls arborícolas para a captura de formigas e mensuramos as seguintes variáveis ambientais: riqueza de árvores, densidade de árvores, altura de árvores, circunferência basal das plantas e cobertura de dossel. Somente a cobertura de dossel apresentou efeito negativo na riqueza de formigas arborícolas. Provavelmente, as características da vegetação e a composição de espécies de plantas são mais homogêneas no candeial, o que explica a ausência de relação entre a riqueza de formigas e as outras variáveis ambientais. Formações abertas abrigam um grande número de espécies oportunistas e generalistas, além de formigas especialistas de climas quentes. O aumento na cobertura de dossel diminui a incidência solar o que pode causar diferenças microclimáticas que afetam negativamente as espécies de formigas especialistas de hábitats abertos. A cobertura de dossel regula a riqueza de espécies de formigas arborícolas em áreas abertas e poucas espécies nestes locais estão aptas a colonizar locais com a vegetação densa. Assim, a maioria das espécies estão presentes em locais com alta temperatura e luminosidade. Em outras palavras, em hábitats de vegetação aberta a relação entre características da vegetaç...

Disentangling elevational richness: a multi‐scale hierarchical Bayesian occupancy model of Colorado ant communities

“…As richness patterns are direct products of species' elevational ranges, the distribution of thermal preferences has a large impact; our results suggest a strong effect of the evolutionary temperature preferences of a taxon -here at temperatures in the lower third of the gradient -diffused through some combination of selection and drift as species have diverged, on current richness patterns. Ant richness tended to decline with increased habitat complexity, as measured by canopy cover, possibly due to less effective chemical trails, less efficient travel, or less available heat, a deterrent to opportunistic or generalist ants (Hölldobler and Wilson 1990, Lassau and Hochuli 2004, Queiroz and Ribas 2016. However, the opposite has also been documented, attributed to abundant nesting and foraging sites (Andersen 1986, Pacheco andVasconcelos 2012).…”

“…Habitat heterogeneity affects species diversity given any degree of specialization, but does not follow a consistent elevational pattern. The relevant habitat complexity axes depend on the focal taxon (Rosenzweig 1995, Stein et al 2014, and for ants, proposed variables include litter depth (Bharti et al 2013), undergrowth structure (Lassau andHochuli 2004, Pacheco andVasconcelos 2012), tree density (Queiroz and Ribas 2016), and canopy cover (Lassau and Hochuli 2004, Pacheco and Vasconcelos 2012, Queiroz and Ribas 2016. While area is partly consistent as a driver of ant elevational richness (Sanders 2002, Bishop et al 2014, Szewczyk and McCain 2016, even the direction of any effect of habitat complexity on ant richness is unclear, with decreases attributed to less efficient movement or chemical signaling (Lassau and Hochuli 2004), and increases to more varied niche space (Andersen 1986, Pacheco andVasconcelos 2012).…”

Ant fauna associated with areas under the direct impact of small hydropower plants in the state of Paraná, Brazil

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Cambio de uso de suelo, manejo forestal y sus implicaciones en las interacciones bióticas asociadas a Cedrela odorata Linnaeus, Meliaceae

“…En ambientes perturbados, la diversidad de hormigas asociadas a la vegetación puede estar afectada por la disminución de la cobertura vegetal, las prácticas de manejo y el uso de fertilizantes y herbicidas (Roth et al, 1994;Perfecto y Snelling, 1995;Power, 1996;Perfecto et al, 1997). Por otro lado, algunos gremios o especies de hormigas omnívoras oportunistas pueden ser favorecidas por las perturbaciones antrópicas en los hábitats (Schreven, 2013;Queiroz y Ribas, 2016;Vanthomme et al, 2016). En este sentido las hormigas pueden jugar un papel importante como bioindicadores de la perturbación en el ecosistema, debido a su alta diversidad y abundancia, a la variedad de nichos que ocupan y a su rápida respuesta a cambios ambientales (Peck et al, 1998;Cuautle et al, 2016).…”