Larval assemblages of large saproxylic cerambycids in Iberian oak forests: wood quality and host preference shape resource partitioning

Abstract

size, altitude and sun exposure. Wood quality and host preference were major factors segregating interspeciic resource partitioning. Cw was prevalent on cork oak decayed wood, and Pm on holm oak degraded wood. Host tree part was involved in Cerambyx larval niche segregation, with Cw prevalent in the fork/branches and Cc in the trunk/base. Pm was never found inhabiting deciduous oaks. Our results may be useful to improve sustainable forest management practices in Iberian oak open woodlands.Abstract Oak open woodlands are widespread in southwestern Iberia and present outstanding ecological, biodiversity and socio-economic values. Evergreen species (holm and cork oaks) are prevalent but deciduous oaks may be also locally important. Three large xylophagous cerambycids are associated to these oaks, Cerambyx welensii (Cw), C. cerdo (Cc) and Prinobius myardi (Pm). Like other saproxylic insects, these cerambycids are essential to the nutrient cycle, wood degradation and tree hollow formation, signiicantly contributing to biodiversity in oak forests. These cerambycids may also potentially colonise healthy living trees and become harmful or pest species. Factors driving their larval ecology are almost unknown, especially in oak forests harbouring mixed populations living in sympatry. Wood samples (n = 500 bolts) from 348 colonised trees were examined during 2011-2016 across the Extremadura region (41,634 km 2 ). Bolts were measured, scored into ive wood quality classes, dissected, and all target cerambycids were collected, measured, reared and taxonomically identiied. We then determined species-speciic prevalence, niche breadth, niche overlap, age structure and population density depending on wood quality, host preference, tree part, wood Electronic supplementary material The online version of this article (

Adult size and sex ratio variation ofCerambyx welensii(Coleoptera: Cerambycidae) in Mediterranean oak (Fagaceae) woodlands

“…However, this sun exposure-related behaviour could be more complex than previously supposed, as in the congeneric species C. welensii (our target longhorn), the higher larval densities occur in trees located in colder aspects (Torres-Vila et al . 2017b).…”

“…Insect samples were collected taking advantage of a recent study on the larval ecology of large longhorns living on oaks (Torres-Vila et al . 2017b). Individuals of C. welensii (adults and larvae) were collected over seven consecutive years (2011–2017) in oak tree species, both evergreen (holm oak, Quercus ilex Linnaeus and cork oak, Quercus suber Linnaeus) and marcescent/deciduous (pyrenean oak, Quercus pyrenaica Willdenow and gall oak, Quercus faginea Lamarck).…”

“…Wood quality in each sampled bolt was visually estimated taking advantage of cut wood sections according to a five-class scale: (1) healthy wood in good vegetative condition, (2) decayed wood: fresh wood in poor physiological condition, (3) degraded wood: appearance and consistency of wood visibly altered, (4) dying wood: wood degradation extreme but wood still living, and (5) dead wood (see Torres-Vila et al . 2017b for additional details). Note that several (or all) of these five wood quality stages may occur simultaneously in a single veteran tree and even in the same tree bolt.…”

“…2005; Torres-Vila et al . 2017b) as they have restricted mobility within hosts and are unable to move between hosts to improve their own nutritional status when food supply or other life conditions deteriorate. In addition, digestion of low-quality woody tissues is costly, which as a rule decreases larval growth rate and extends development time – two major determinants of adult size (Mirth and Riddiford 2007).…”

Mapping oak shoot browning in SW Spain using online imagery as virtual prospecting tool

“…Most lowland oak forests in this area have experienced a huge man-made transformation for several centuries, so their primaeval climax stage has almost completely disappeared. At present, oak forests occur as a typical open woodland similar to the savannah landscape, the so-called dehesa in Spain and montado in Portugal, which sustains a traditional agro-silvo-pastoral use shaping landscape multiplicity (Blondel 2006;Bugalho et al 2011;Torres-Vila et al 2017). Open oak woodlands present outstanding ecological and socioeconomic values (Montero et al 1998;Moreno and Pulido 2009) and host the highest levels of biological diversity in Europe (Cowling et al 1996;Ramírez-Hernández et al 2014;Vodka et al 2009), so they are considered a biodiversity hotspot (Medail and Quezel 1999;Myers et al 2000).…”