Conservation implications for metapopulation genetics in the
Amazon Forest
Anthropogenic activities are the main cause of forest conversion
associated with the change in land use in Amazonia over recent decades
(Curtis et al., 2018). Forest fragmentation due to commodity-driven
deforestation represents the most immediate threat to the Amazonia, the
synergist effects of forest loss and forest degradation (edge effects,
logging, fires, and droughts) put in threaten forest ecosystems and
services with nearly 38% of the forests in the region currently
degraded (Chase et al., 2020; Lapola et al., 2023). Even if conservation
policies with objectives of zero deforestation in the Amazon are reached
by 2030, a landscape of isolated patches will remain for decades
(Fischer et al., 2021).
Research efforts have been focused on determining the habitat amount, in
terms of patch size and isolation, that fragmented landscape allows for
biodiversity maintenance of a region (Fahrig et al., 2019, 2022; Watling
et al., 2020). Conservation management debates whether efforts should be
given to preserving a single large patch or several small patches
(SLOSS: single large or several small) (Diamond, 1975; Tjørve, 2010).
The BDFFP has focused on addressing this question, with a myriad of
studies targeting different organisms, indicating an Amazonian
biodiversity loss after a threshold habitat size and isolation (Laurance
et al., 2011, 2018). From the organisms that have been studied at the
BDFFP, few have related the demographic consequences on the evolutionary
processes (drift and migration) that impact the population genetic
structure in a fragmented landscape (Hamilton, 1999; Côrtes et al.,
2013; Zartman et al., 2006). This has left a gap when addressing the
amount of habitat for conservation genetics. In long-lived organisms,
the distribution of genotypes observed in fragmented habitats is
expected to reflect the historical landscape configuration, demographic
patterns, and population connectivity (Carley et al., 2022).
Consequently, in most long-lived organisms this association is
challenging, but annual plants such as understory Heliconia(Côrtes et al., 2013) and patch-tracking epiphyllous metapopulation
(Zartman et al., 2006) have been important in our understanding of the
genetic consequence of habitat fragmentation.
Herein, we integrate demographic and genetic data of epiphyllous
metapopulation to quantify threshold patch size for population viability
and genetic maintenance for regional conservation management taking into
consideration the functional connectivity. Our results support the
maintenance of genetic diversity in small patches (>10-ha)
when asymmetric migration allows for rescue effects of extinct genotypes
among patches in a fragmented landscape (Hufbauer et al., 2015). This
has large implications for conservation where growing knowledge points
to biodiversity managers prioritizing demographic and genetic rescue
effects of populations when designating conservation areas and targeting
declining populations in degraded habitats (Hufbauer et al., 2015;
Hanski et al., 2015; Auffret et al., 2017; Carley et al., 2022).
Evidence-based conservation strategies in the Amazon Forest require
spatial configuration of (>100–10 000-ha) large patches of
non-degraded forests (Laurance et al., 2018), that will allow for the
preservation of long-term evolutionary processes (Carley et al., 2022).