Metacommunity dynamics and the spurious detection of species associations in co-occurrence analyses: patch disturbance matters

Many methods attempt to detect species associations from co-occurrence patterns. Such associations are then typically used to infer inter-specific interactions. However, correlation is not equivalent to interaction. Habitat heterogeneity and out-of-equilibrium colonization histories are acknowledged to cause species associations even when inter-specific interactions are absent. Here we show how classical metacommunity dynamics, within a homogeneous habitat at equilibrium, can also lead to statistical associations. This occurs even when species do not interact. All that is required is patch disturbance (i.e. simultaneous extinction of several species in a patch) a common phenomenon in a wide range of real systems. We compare direct tests of pairwise independence, matrix permutation approaches and joint species distribution modelling. We use mathematical analysis and example simulations to show that patch disturbance leads all these methods to produce characteristic signatures of spurious association from "null" co-occurrence matrices. Including patch age (i.e. the time since the last patch disturbance event) as a covariate is necessary to resolve this artefact. However, this would require data that very often are not available in practice for these types of analyses. We contend that patch disturbance is a key (but hitherto overlooked) factor which must be accounted for when analysing species co-occurrence.

CRM performance and development of media entrepreneurship in digital, social media and mobile commerce

Purpose The purpose of this paper is to evaluate the effect of CRM performance and technological innovation on performance of media entrepreneurs considering firm size. Design/methodology/approach This is an analytical study used to empirically test the hypotheses proposed for SEM techniques using PLS and R packages. It used two steps in this way: the assessment of the outer model and the assessment of the inner model. Moreover, a bootstrapping method was employed to test indirect effects. Data were collected by distributing 127 questionnaires between the managers and deputies of active firms across Rasht, Iran. Findings The effect of CRM performance on SMEs performance development is partially mediated by media entrepreneurship. Moreover, the effect of technological innovation on SMEs performance development is mediated by media entrepreneurship. Furthermore, permutation test results indicated that there is no significant difference between small- and medium-sized firms. Research limitations/implications This study used cross-sectional sampling method that can seriously limit result generalization. Therefore, conducting longitudinal studies is strongly recommended. Practical implications The results of IPMA matrix indicated the serious importance of technological innovation, as a variable with the highest importance for SMEs performance development. Nevertheless, this variable has received the lowest importance in the studied population. Therefore, SMEs’ managers should pay sufficient attention to the concepts of “product innovations” and “process innovations.” Originality/value This study is of high importance in that it has adopted new and effective indices for statistical analysis. IPMA matrix, permutation test, CTA and FIMIX are examples. In addition, plspm and Matrixpls packages in R were used for the first time in this study.