Changes in a peri‐urban butterfly assemblage over 80 years near Melbourne, Australia

Abstract

Although changes, particularly declines, in Australian terrestrial insects and other invertebrates have long been suspected and well‐documented for some species, the magnitude, rate and spatial extent of decline remain unclear. Here we use a combination of alternative, qualitative approaches (expert opinion, historical records and temporal replication of surveys) to standardised monitoring and mapping programs to investigate the extent of change of a peri‐urban butterfly assemblage. This assemblage, comprising 52 species, of which 46 are residents or seasonal immigrants, was studied at three spatial scales (local ~0.01 km2, intermediate ~9 km2 and regional ~100 km2) in the Eltham district near Melbourne based on presence/absence data over the past 40 (1981–2020) and 80 years (1941–2020). We then consider the causal factors or drivers that have led to changes, and we explore the timing and ecological patterns underpinning extirpations. Long‐term records reveal substantial changes (mostly decline) in composition and species richness of the 46 breeding species at all spatial scales and time frames analysed. Although the magnitude and rate of decline were higher at the smaller, local to intermediate scales (29–43% decline over 40 years, loss rate of 0.20–0.25 species/year) compared with the larger, regional scale (26% decline over 80 years, loss rate of 0.15 species/year), extirpations at the larger scale were more alarming because they are indicative of widespread population collapse. Declines in relative abundance and occupancy were also recorded at the intermediate and regional spatial scales. Further decline (extinction debt) is anticipated for several ecological specialists currently known from very few sites. Historical extirpations mostly involved obligate myrmecophilous lycaenids and appear to have been largely driven by a combination of urbanisation (habitat loss, degradation and fragmentation) and vegetation encroachment. More recent extirpations consist mainly of grass‐feeding and mistletoe‐feeding specialists and are more worrying because they have predominantly occurred within the past 20–30 years. An interaction of urbanisation (tree canopy death and decline of mistletoes and their host trees from ecosystem dysfunction) and climate change (water stress and heat waves) are considered to be the most likely drivers for these ecological guilds.

Impact of reserve area on reproduction of a moth‐pollinated Stackhousia Sm. (Celastraceae) species in a fragmented landscape

“…It is hypothesized that this lack of marked spatial variability in reproduction is due to effective pollination by common, night-flying moths, which can more or less utilize the reserves and surrounding matrix to complete their life cycle(s). Nevertheless, more recent declines in once common butterfly (Braby et al, 2021) and moth species (Green et al, 2021) in areas of southern Australia raise concerns about future pollinator abundance and diversity in the study region.…”

“…Importantly, it should be said the above arguments do not imply that there have not been declines in the abundance and diversity of moths within the study region. The local abundance and diversity of Lepidoptera have certainly declined due to landscape disturbance and related anthropogenic impacts within southern Australia (Braby et al, 2021), and smaller reserves may be less diverse in their Lepidopteran assemblages than larger ones (Williams, 2009(Williams, , 2011. However, potential differences in the abundance and diversity of floral visitors among reserves is not resulting in marked differences in the measured reproductive output of S. aspericocca ssp.…”

Island Hopping through Urban Filters: Anthropogenic Habitats and Colonized Landscapes Alter Morphological and Performance Traits of an Invasive Amphibian

“…Although uncommon for most toad species, increased climbing ability has been observed in cane toads, which is related to changes in habitat structure and food availability during invasions [ 51 ]. We would assert that these factors likely played a role in the expression of this trait within guttural toads since urban habitats in both the native and invasive ranges are fraught with potential barriers to terrestrial movement (e.g., fences, infrastructure, and other anthropogenic features [ 82 , 83 , 84 ] and differences in prey availability and niche openness (e.g., between urban and natural sites [ 85 , 86 ]. We also posit, however, that this shift may be linked to antipredator behaviors toward anthropogenically associated terrestrial threats (e.g., subsidized predators, pets, lawnmowers and other hazardous garden equipment, and people) that are distinct from those used in response to predators that evolved within the native range of this toad species.…”