Habitat amount, not patch size and isolation, drives species richness of macro‐moth communities in countryside landscapes

Abstract

Aim Our aim was to test whether species richness patterns are best explained by the effect of the total amount of habitat within the landscape, or instead by a combination of patch size and patch isolation effects. To this end, we jointly contrast the habitat amount hypothesis and countryside biogeography with patch size and isolation concepts from island biogeography. Location Three multi‐habitat landscapes in Peneda‐Gerês National Park, NW Portugal. Taxon Macro‐moths (Lepidoptera). Methods Light‐trapping using a semi‐nested design at 84 fixed sites which were each repeatedly sampled six times. Results Autocovariate models show that sampling sites with a higher number of forest and meadow macro‐moth species (alpha diversity) were surrounded by a higher amount of forest and meadow habitat, respectively within a 160 and 320 m radius (scale of effect). These top‐ranked models, containing only habitat amount as a significant variable, had lower Akaike's information criteria (AIC) than models (only) containing patch size and/or isolation. Complementary to this, the countryside species–area relationship (SAR) model outperforms the classic SAR model, so that the effective area of habitat explains landscape species richness (gamma diversity) across spatial scales (beta diversity) better than the classic SAR. Specifically, we show that forest macro‐moths have a higher spatial turnover than meadow macro‐moths and that, on average, there are more species in forest than in meadow habitat. Main conclusions The habitat amount hypothesis predicts alpha species richness in multi‐habitat landscapes better than do patch size and isolation while the countryside SAR predicts beta and gamma diversity better than the classic SAR. We suggest that evidence is mounting to revise the application of the classical approaches of island biogeography and metapopulation theory to conservation biogeography.

Relationship between moth (night active Lepidoptera) diversity and vegetation characteristics in southern Sweden

“…The results also suggest a higher moth richness and abundance in wooded sites than in open grasslands, as previously also found by e.g. Merckx et al (2012Merckx et al ( , 2019.…”

“…In Sweden, conservation assessments of grassland habitats are generally based on vascular plants, sometimes with the addition of some in comparison species-poor insect groups such as bees and butterflies and forest assessments are mostly based on cryptogams. However, in both habitat types, and in particular in temperate forests, moths are richly represented, take part in vital ecological processes (Truxa and Fiedler 2012a;Infusino and Scalerico 2018;Merckx et al 2019) and deserve more conservation attention (Ballesteros-Mejia et al 2017). This in particular since there are indications that moth diversity may accurately reflect conservation values (Uhl et al 2016;Zou et al 2016).…”

“…While there are quite some recent studies of relationships between moth diversity and environmental gradients or characteristics in tropical and Mediterranean habitats (e.g. Axmacher et al 2004Axmacher et al , 2009Beck et al 2011;Uhl et al 2016;Merckx et al 2019), there are only few such studies in temperate or boreal landscapes (e.g. Littlewood 2008;Highland et al 2013;Horvath et al 2016;Zou et al 2016) and hardly any from the Nordic region.…”

Marked compositional changes in harvestmen assemblages in Amazonian forest islands induced by a mega dam

“…Although the species-area relationship is one of the few ironclad rules in ecology (Mathews et al 2016), we found that area failed in explaining richness patterns for harvestmen assemblages, the absence of this relationship has been documented before 1 for this group in Amazonian upland forest sites where microhabitat structure and availability per unit area also explained patterns of harvestmen species composition but not species richness in harvestmen assemblages (Colmenares et al, 2016). The same pattern was also found for other arthropods, such as macro-moth communities in temperate woodland countryside landscapes, although in that case habitat amount, rather than patch size and isolation were the main drivers of species richness (Merckx et al, 2019), both however have not explained it for harvestmen either. Harvestmen species richness may not be responding to any of the most common predictor variable collectively but individually some severe richness reduction occurred in the fragmented Island mosaic in Balbina lake, on the other hand there are some species apparently benefiting of the fragmentation effects promoted by the dam.…”

Saproxylic species are linked to the amount and isolation of dead wood across spatial scales in a beech forest

“…While some studies testing the habitat amount hypothesis have found support for it (e.g. birds: De Camargo et al 2018; small mammals: Melo et al 2017; macro-moths: Merckx et al 2019;saproxylic beetles: Seibold et al 2017;multiple species: Watling et al 2020), others have rejected it (e.g. plants: Evju and Sverdrup-Thygeson 2016; Lindgren and Cousins 2017; micro-arthropods: Haddad et al 2016;birds: Kormann et al 2018) or found different results for different taxonomic groups (frogs and reptiles: Pulsford et al 2017).…”