Pseudoreplication in Tropical Forests and the Resulting Effects on Biodiversity Conservation

Abstract

Tropical forest ecosystems are threatened by habitat conversion and other anthropogenic actions. Timber production forests can augment the conservation value of primary forest reserves, but studies of logging effects often yield contradictory findings and thus inhibit efforts to develop clear conservation strategies. We hypothesized that much of this variability reflects a common methodological flaw, simple pseudoreplication, that confounds logging effects with preexisting spatial variation. We reviewed recent studies of the effects of logging on biodiversity in tropical forests (n = 77) and found that 68% were definitively pseudoreplicated while only 7% were definitively free of pseudoreplication. The remaining proportion could not be clearly categorized. In addition, we collected compositional data on 7 taxa in 24 primary forest research plots and systematically analyzed subsets of these plots to calculate the probability that a pseudoreplicated comparison would incorrectly identify a treatment effect. Rates of false inference (i.e., the spurious detection of a treatment effect) were >0.5 for 2 taxa, 0.3-0.5 for 2 taxa, and <0.3 for 3 taxa. Our findings demonstrate that tropical conservation strategies are being informed by a body of literature that is rife with unwarranted inferences. Addressing pseudoreplication is essential for accurately assessing biodiversity in logged forests, identifying the relative merits of specific management practices and landscape configurations, and effectively balancing conservation with timber production in tropical forests.

Slow recovery of a secondary tropical forest in Southeast Asia

“…Analyses that lack true treatment replicates are susceptible to spurious relations between two variables that are in fact driven by a spatial gradient, or a third variable that maps to the spatial gradient (Fortin and Gurevitch, 2001;Legendre and Legendre, 1998;Ramage et al, 2013). Despite this reality, the vast majority of studies that address similar questions are pseudoreplicated and devoid of any efforts to account for underlying variation (Ramage et al, 2013).…”

“…Analyses that lack true treatment replicates are susceptible to spurious relations between two variables that are in fact driven by a spatial gradient, or a third variable that maps to the spatial gradient (Fortin and Gurevitch, 2001;Legendre and Legendre, 1998;Ramage et al, 2013). Despite this reality, the vast majority of studies that address similar questions are pseudoreplicated and devoid of any efforts to account for underlying variation (Ramage et al, 2013). In contrast, we used partial Mantel tests to distinguish the effects of forest age class (primary vs. secondary) from pre-existing spatial and elevation gradients; as such, this paper also serves to demonstrate how meaningful inferences about treatment effects can be drawn from a dataset that lacks true treatment replication.…”

“…If differences in the dependent variables between forest age classes simply reflect a relatively smooth spatial gradient or are highly affected by elevation, measures of diversity and composition should not be significantly associated with age class after accounting for spatial or elevation distances. This method for addressing the lack of true treatment replication, is relatively simple but rarely used in similar studies (Ramage et al, 2013). Statistical analyses were done using R statistical software v2.13.2 (R Core Team, 2013).…”

Evidence for insect seed predator dynamics mediated by vertebrate frugivores

“…Clearly, spatial replication would have greatly strengthened these arguments, given that the obser ved differences between the two tracts could also be related to tract-specifi c features other than cattle presence or absence (see Ramage et al 2012). Nevertheless, the frugivory explanation for the observed between-tract changes in seed predation levels and seed predator species composition is the most parsimonious.…”

Systematic review of effects on biodiversity from oil palm production

“…One way to account for the variability is to include replication in the study design. Unfortunately, the majority of the studies included in the review included insufficient reporting of study conditions and details, or were poorly replicated or pseudo-replicated, which is common for biodiversity studies (Ramage et al 2013). Although it is assumed that site comparison studies pair sites that share common attributes, this is not necessarily the case in practice.…”