Temporal stability in species richness but reordering in species abundances within avian assemblages of a tropical Andes conservation hot spot.

Boris A Tinoco,Steven C Latta,Andrea Nieto,Catherine H Graham,Pedro X Astudillo

doi:10.1111/btp.13016

Abstract

As the pace of environmental change increases, there is an urgent need for quantitative data revealing the temporal dynamics of local communities in tropical areas. Here, we quantify the stability of avian assemblages in the highly threatened, but poorly studied, Andean biodiversity hot spot. We evaluated the temporal variation in species richness and community composition of local bird assemblages in three habitat types (native forest, introduced forest, native shrub) using a unique, relatively long‐term data series from Cajas National Park and Mazán Reserve in the southern Andes of Ecuador. We sampled birds with mist nets using a standardized protocol over 11 years, from 2006 to 2016. Species richness remained stable over time across habitats, but community composition changed in the native forest. In particular, we observed taxonomic reordering in the native forest, in which the evenness in the distribution of abundances of taxa decreased over time. This finding is consistent with other studies where species richness remained constant over time while community composition changed. Our study highlights the value of long‐term studies in the tropical Andes as we show that species composition of birds in a montane forest is changing, consistent with global trends in biodiversity change.

Highlights

The increasing pace of environmental change has resulted in a rapid decline of populations, range shifts, and, in some cases, extinctions over the last century (Barnosky et al, 2011; Rosenberg et al, 2019)
Drivers of environmental change, such as climate and land-use change, can influence temporal variation in local communities, where changes are generally quantified in terms of species richness and community composition (Magurran & Henderson, 2010; Newbold et al, 2020)
Observed annual species richness did not change in any of the habitats over time (Figure 3a). These results are not influenced by sampling artifacts as the detectability of species richness has been constant over time

Summary

| INTRODUCTION

Newbold et al, 2020), hindering our ability to quantify the patterns of variation in species richness and composition needed to identify generalities in the responses of biodiversity to global change. Cajas National Park and the nearby Mazán reserve, located in southern Ecuador, harbor a representative avifauna of high- elevation tropical Andean ecosystems and have been recognized as an important bird conservation area (Astudillo et al, 2015; Freile & Santander, 2005) Previous work in this area reported a decline in bird species richness in native and introduced forest habitats. We expect a temporal decline in composition similarity across different habitats, corresponding to the global trend of local community composition change over time (Blowes et al, 2019; Dornelas et al, 2014); (3) Is the change in species composition a result of turnover and/or the reordering of species (i.e., changes in abundances)? There has been little change in the structure of the vegetation in all habitat types over the period of this study (Tinoco et al, 2019)

| METHODS

| RESULTS

| DISCUSSION