Comments on Bartolino et al. (2011): limits of cumulative relative frequency distribution curves for hotspot identification

Abstract

The recent paper by Bartolino et al. (Popul Ecol 53:351–359, ) presents a new method to objectively select hotspots using cumulative relative frequency distribution (CRFD) curves. This method is presented as being independent from the selection of any threshold and, therefore, less arbitrary than traditional approaches. We argue that this method, albeit mathematically sound, is based on likewise arbitrary decisions regarding threshold selection. Specifically, the use of the CRFD curve approach requires the occurrence of two criteria for the method to be applied correctly: the selection of a 45° tangent to the curve, and the need to consider the highest relative value of the study parameter corresponding to a 45° slope tangent to the curve. Using two case studies (dealing with species richness and abundance of a particular species), we demonstrate that these two criteria are really unrelated to the underlying causes that shape the spatial pattern of the phenomena under study, but rather related to sampling design and spatial scale; hence, one could likewise use different but valid criteria. Consequently, the CRFD curve approach is based on the selection of a pre‐defined threshold that has little, if any, ecological justification, and that heavily influences the final hotspot selection. Therefore, we conclude that the CRFD curve approach itself is not necessarily better and more objective than any of the global methods typically used for hotspot identification. Indeed, mathematical and/or statistical approaches should not be viewed as a panacea to solve conservation problems, but rather used in combination with biological, practical, economic and social considerations.

Assessing hotspots within hotspots to conserve biodiversity and support fisheries management

“…Hotspots, for example, may contain a certain percentage of the target species or grid cells with the highest values (Myers et al 2000) or sites with values >1 SD above the mean (Santora & Veit 2013). The choice of a criterion ultimately depends on the respective case study, and it will always have some degree of subjectivity (Cayuela et al 2011).…”

Renewal of the editorial office and board

“…A 'Notes and Comments' article would be (a) brief notes on both empirical and theoretical investigations (see Ramesh et al 2013 in this issue for an example), or (b) critical comments on previously published papers to develop further discussion (see DeVink et al 2011;McKelvery et al 2011;Hargrove et al 2011;Cayuela et al 2011). A 'Forum' article would be (a) discussions on new concepts, analyses and data that are significant for population ecology (see Ma 2011), or (b) a short review or a review in a small arena.…”

Frequency distribution curves and the identification of hotspots: response to comments

“…This is a response to the criticism by Cayuela et al (2011) of our proposal for a frequency distribution approach to the identification of hotspots in conservation and ecology.…”

“…The main criticism from Cayuela et al (2011) does not concern or affect the validity of the method per se, but mainly relates to a presumed lack of objectivity in the identification of a spatially global threshold derived from geometric properties of cumulative relative frequency distribution (CRFD) curves. As we will demonstrate, their critique mainly originates from the loose biological/ecological meaning of hotspots, and from misreading and misinterpreting the methodology we proposed.…”

“…Moreover, the identification of hotspots is mostly driven by practical, socioeconomic or conservation objectives, partially accounting for the properties of the spatial processes under investigation. Cayuela et al (2011) based their criticism of our paper on the widely recognised difficulty involved in adequately defining hotspots. In particular, they claim that our method is as subjective as any other global method (sensu Nelson and Boots 2008), because the hotspots identified using CRFD curves have no particular ecological meaningalthough we have never claimed that they do.…”