The impact of secondary forest regeneration on ground-dwelling ant communities in the Tropical Andes

Abstract

Natural regeneration of abandoned farmland provides an important opportunity to contribute to global reforestation targets, including the Bonn Challenge. Of particular importance are the montane tropics, where a long history of farming, frequently on marginal soils, has rendered many ecosystems highly degraded and hotspots of extinction risk. Ants play crucial roles in ecosystem functioning, and a key question is how time since abandonment and elevation (and inherent temperature gradients therein) affect patterns of ant recovery within secondary forest systems. Focusing on the Colombian Andes across a 1300 m altitudinal gradient and secondary forest (2–30 years) recovering on abandoned cattle pastures, we find that over time ant community composition and species richness recovered towards that of primary forest. However, these relationships are strongly dependent on elevation with the more open and warmer pasturelands supporting more ants than either primary or secondary forest at a particular elevation. The loss of species richness and change in species composition with elevation is less severe in pasture than forests, suggesting that conditions within pasture and its remaining scattered trees, hedgerows and forest fragments, are more favourable for some species, which are likely in or near thermal debt. Promoting and protecting natural regenerating forests over the long term in the montane tropics will likely offer significant potential for returning ant communities towards primary forest levels.Electronic supplementary materialThe online version of this article (10.1007/s00442-019-04497-8) contains supplementary material, which is available to authorized users.

Microclimate buffering and thermal tolerance across elevations in a tropical butterfly

“…Any habitat change that affects forest heterogeneity could reduce its large temperature buffering potential (Blonder et al, 2018;Jucker et al, 2020), and butterfly diversity as a whole (Montejo-Kovacevich et al, 2018). Nevertheless, microclimates have been shown to recover decades after low impact land-uses (González del Pliego et al, 2016;Mollinari et al, 2019;Senior et al, 2018), allowing for recolonization of biodiversity (Hethcoat et al, 2019). This highlights the need to protect degraded secondary forest, as these are now more abundant than primary forests in most of the tropics (Edwards et al, 2011;Senior et al, 2017).…”

Little trace of floristic homogenization in peri‐urban Andean secondary forests despite high anthropogenic transformation

“…The ubiquity of anthropogenic pressures in tropical regions is the primary threat to biodiversity, and one of the most significant challenges humanity is currently facing (Lewis et al, 2015). Hope is set on regrowing secondary forests, which may serve as habitat refugia for many species and play a central role in ecosystem functioning (Hethcoat et al, 2019). Secondary forests currently account for over half of the world's tropical forests, and their distribution is expanding as they gradually replace old-growth stands that have been clear-cut for productive use, but subsequently abandoned (Chazdon et al, 2016).…”

Reported climate change impacts on cloud forest ants are driven by sampling bias: A critical evaluation of Warne et al. (2020)

“…While climatically driven elevational shifts have been documented for some invertebrate groups (e.g., moths moving up by 67 m in 40 years (Chen et al, 2009)), recent studies highlight the importance of consistent sampling methods and timing: if such methodological variance is considered, range shifts can appear to be less pronounced (Cheng et al, 2019) or driven by natural seasonality (Maicher et al, 2020). For cloud forest ant assemblages, several recent studies that consider both habitat change and elevation found that the mountain assemblages are more robust to vegetation changes than their lowland counterparts (Hethcoat et al, 2019; Mottl et al, 2019). This paints a more optimistic picture that mountain ants in these tropical environments might be perhaps also less sensitive to climatic changes.…”