Diversity patterns of herbivores have been related to climate, host plant traits, host plant distribution and evolutionary relationships individually. However, few studies have assessed the relative contributions of a range of variables to explain these diversity patterns across large geographical and host plant species gradients. Here we assess the relative influence that climate and host plant traits have on endophagous species (leaf miners and plant gallers) diversity across a suite of host species from a genus that is widely distributed and morphologically variable. Forty-six species of Acacia were sampled to encapsulate the diversity of species across four taxonomic sections and a range of habitats along a 950 km climatic gradient: from subtropical forest habitats to semi-arid habitats. Plant traits, climatic variables, leaf miner and plant galler diversity were all quantified on each plant species. In total, 97 leaf mining species and 84 plant galling species were recorded from all host plants. Factors that best explained leaf miner richness across the climatic gradient (using AIC model selection) included specific leaf area (SLA), foliage thickness and mean annual rainfall. The factor that best explained plant galler richness across the climatic gradient was C:N ratio. In terms of the influence of plant and climatic traits on species composition, leaf miner assemblages were best explained by SLA, foliage thickness, mean minimum temperature and mean annual rainfall, whilst plant gall assemblages were explained by C:N ratio, %P, foliage thickness, mean minimum temperature and mean annual rainfall. This work is the first to assess diversity and structure across a broad environmental gradient and a wide range of potential key climatic and plant trait determinants simultaneously. Such methods provide key insights into endophage diversity and provide a solid basis for assessing their responses to a changing climate.
"airly uniform conditions along the Pacific Ocean to more extreme and variable conditions inland ( Rotenberry , 1978 ; Ohmann & Spies , 1998 ) . Indeed , Progar and Schowalter ( 2002 ) , found significant changes in canopy arthropod assemblages asso - ciated with a precipitation gradient in old - growth forest of Washington and Oregon . Similarly , Bairstow et al . ( 2010 ) found that herbivore species richness varied with climate and plant traits in a coastal – inland gradient in eastern Australia . What is less clear is whether coastal - interior gradients interact with latitude to shape patterns of arthropod diversity or herbivore pressure . The goal of this study was to compare the influence of latit"
[Show abstract][Hide abstract] ABSTRACT: A classic pattern in biogeography is the decline in species richness from lower to higher latitudes. Communities, however, can also vary with other geographical patterns, such as the abiotic gradients that occur from coastal to interior habitats.In this study, we surveyed arthropod communities and herbivore pressure on populations of a dominant shrub, Baccharis pilularis, across a 2000 km latitudinal transect to determine whether coastal versus interior location mediates arthropod responses to latitude.We found that arthropod species richness and abundance declined with increasing latitude. We also found significant coastal-interior shifts in community composition and trophic structure. Specifically, predator and scavenger richness were two and three fold greater at coastal sites compared to interior sites, and were three- and six-fold more abundant on the coast than in the interior. Herbivore pressure displayed a similar pattern, with greater abundance at lower latitudes and at coastal sites.Our results corroborate the general macroecological pattern that diversity declines with increasing latitude, and that coastal versus interior location can also shape community assemblages. We did not, however, find any interaction between latitude and location suggesting the effect of latitude on arthropod communities remains consistent inland compared to more constant coastal conditions.
"For most extant endophytic feeding, it is well known that many insect species make single, distinct DTs on single host species at a site , , , , . However, external feeders (leaf-chewers; Figs. "
[Show abstract][Hide abstract] ABSTRACT: The fossil record demonstrates that past climate changes and extinctions significantly affected the diversity of insect leaf-feeding damage, implying that the richness of damage types reflects that of the unsampled damage makers, and that the two are correlated through time. However, this relationship has not been quantified for living leaf-chewing insects, whose richness and mouthpart convergence have obscured their value for understanding past and present herbivore diversity. We hypothesized that the correlation of leaf-chewing damage types (DTs) and damage maker richness is directly observable in living forests. Using canopy access cranes at two lowland tropical rainforest sites in Panamá to survey 24 host-plant species, we found significant correlations between the numbers of leaf chewing insect species collected and the numbers of DTs observed to be made by the same species in feeding experiments, strongly supporting our hypothesis. Damage type richness was largely driven by insect species that make multiple DTs. Also, the rank-order abundances of DTs recorded at the Panamá sites and across a set of latest Cretaceous to middle Eocene fossil floras were highly correlated, indicating remarkable consistency of feeding-mode distributions through time. Most fossil and modern host-plant pairs displayed high similarity indices for their leaf-chewing DTs, but informative differences and trends in fossil damage composition became apparent when endophytic damage was included. Our results greatly expand the potential of insect-mediated leaf damage for interpreting insect herbivore richness and compositional heterogeneity from fossil floras and, equally promisingly, in living forests.
PLoS ONE 05/2014; 9(5):e94950. DOI:10.1371/journal.pone.0094950 · 3.23 Impact Factor
"In the present paper, we have removed major climatic influences on anatomical variation by collecting from the same geographical area within the temperate zone. The species from these temperate sites have recently been used in a study of plant galler and leaf miner species richness (Bairstow et al. 2010). In future work, we will widen our survey to include species from arid, semiarid and subtropical climate zones. "
[Show abstract][Hide abstract] ABSTRACT: Abstract
Acacia s.s. comprises approximately 1020 species (i.e. just under one-third of all mimosoid legumes) and is almost entirely restricted to, although widespread, on the Australian continent. We investigated variation in the wood anatomy of 12 species from temperate New South Wales in a study concentrating on four recognised taxonomic sections (Botrycephalae, Juliflorae, Phyllodineae and Plurinerves), to elucidate which characteristics are consistent within the sections, having removed climatic effect as much as possible. The sections had great utility in species identification, whereas none of the wood characters reflected the hypothesised phylogeny of the genus. The main consistent difference among species was in ray width (uniseriate versus 1–3 cells wide). All species had distinct growth rings. The vessels had alternate vestured pitting and simple perforation plates. Fibres were generally thick-walled, and many fibres had a gelatinous inner wall (tension wood fibres) and were inconsistently distributed. Axial parenchyma was mainly paratracheal, ranging from vasicentric to confluent and varied greatly in abundance. Prismatic crystals were usually present in chambered fibres and axial parenchyma strands, and also varied in abundance. The variation in these qualitative characters obscures taxonomic differences, but may allow inferences to be made about environmental adaptation.
Australian Journal of Botany 05/2013; 61(4):291-301. DOI:10.1071/BT13053 · 1.36 Impact Factor
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