Facilitation Among Saproxylic Insects Inhabiting Tree Hollows in a Mediterranean Forest: The Case of Cetonids (Coleoptera: Cetoniidae) and Syrphids (Diptera: Syrphidae)

Abstract

Tree hollows offer an ideal niche for saproxylic insects in mature Mediterranean forests, where Diptera and Coleoptera are the richest groups. Co-occurrence is frequently observed among many species of both groups in these microhabitats, and some of these species have been considered to facilitate the presence of other species by acting as ecosystem engineers. One of the systems that is found in Mediterranean tree hollows is formed by cetonid (Coleoptera: Cetoniidae) and syrphid (Diptera: Syrphidae) larvae. Here, cetonid larvae feed on wood and litter and produce a substrate that is easier to decompose. To assess the possible role of these larvae as facilitating agents for the saproxylic guild, we studied whether the presence of saprophagous Syrphidae inside tree hollows is associated with the activity of cetonid larvae. Furthermore, in laboratory conditions, we tested whether cetonid larvae activity can improve the development and fitness of the saprophagous syrphid species. Our results show that "cetonid activity" was the variable that best explained the presence of saprophagous syrphid species in natural conditions. Myathropa florea (L., 1758) was one of the species most influenced by this activity. The laboratory experiment gave similar results, demonstrating that an enriched substrate with Cetonia aurataeformis Curti, 1913 larval feces improves syrphid larval growth rate and fitness of adults (measured as longer wing length) of M. florea.

El ecosistema de dehesa como reservorio de diversidad de insectos saproxílicos (Coleoptera y Diptera: Syrphidae) y factores que determinan sus ensambles

“…: 13-24 en algún estadio de su ciclo de vida, dependen de varios atributos de la madera muerta o en proceso de descomposición, asociada tanto a árboles moribundos o muertos (en pie o caídos) como a árboles vivos, o de hongos que colonizan dicha madera o bien están asociadas a la presencia de otras especies estrictamente saproxílicas (Speight, 1989;Alexander, 2008) relacionándose con cualquiera de los microhá-bitats ofrecidos por la madera de los árboles (Winter & Möller, 2008;Stokland et al, 2012) y cumpliendo un papel clave en el proceso de reincorporación de nutrientes en el ecosistema (Jönsson et al, 2004;Micó et al, 2011b;Crowther et al, 2012;Sánchez-Galván et al, 2014).…”

“…Es en esta amplia gama de microhábitats donde se producen una serie de interacciones que están condicionadas por la relación entre las características concretas del árbol y la calidad del microhábitat, y la presencia de especies concretas que determinan la presencia de otras. No obstante, se sabe muy poco sobre la importancia de las interacciones entre los distintos gremios tróficos que conviven en los microhábitats que ofrece la madera muerta (Quinto et al, 2012), a pesar de que algunas especies son capaces de favorecer la disponibilidad de recursos para otras especies, al causar cambios físicos o químicos en las características del medio (Jones et al, 1994;Micó et al, 2011b;Sánchez-Galván et al, 2014, Micó et al 2015.…”

Diversity of Cetoniidae (Insecta: Coleoptera) in the Cerrado of Central Brazil

“…In many species, adults are considered pollinators (Singer & Cocucci ; Micó & Galante ; Peter & Johnson ). The larvae are important decomposers, developing in decaying vegetable matter, feces and rotting tree trunks, modifying chemically and physically the substrate and facilitating the development of other saproxylic species (Arce‐Perez & Morón ; Micó & Galante ; Micó et al ; Sánchez‐Galván et al ). In some species of Cetoniidae the larvae live associated with social insects (Krikken ; Micó et al ; Peter & Johnson ; Puker et al ).…”

Chemical transformation of Quercus wood by Cetonia larvae (Coleoptera: Cetoniidae): An improvement of carbon and nitrogen available in saproxylic environments

“…The saproxylic beetle Cetonia aurataeformis Curti (Coleoptera: Scarabaeoidea: Cetoniidae) is a common Iberian species, the larvae of which develop mainly in tree hollows while feeding on fragments of wood and litter. These larvae produce a high volume of easily distinguishable faeces, which remain with the substrate for more than a year [43]. Micó et al [31] reared C. aurataeformis larvae in three different woody substrates (litter, Betula alba wood, and Quercus pyrenaica wood) in laboratory conditions and concluded that larvae were able to digest polysaccharides and lignin, producing a residue richer in nutrients than the original substrate with an organic structure that contains a fraction of lignin that is easier to decompose.…”