Bias files
The ‘presence only’ SDMs are affected by bias sampling, to overcome this
one of the common methods employed is the use of a target group bias
file to restrict background sampling area (Phillips et al. 2009; Syfert
et al. 2013; Vollering et al. 2019). We pooled all occurrence
coordinates of the fish species and adult odonate species with 2 or more
occurrence coordinates to produce target group bias files for both fish
and odonate species respectively. However, we excluded Epiophlebia
laidlawi from the odonate target group since its distribution in Bhutan
is known only from its larval distribution while all other odonate
species are mainly known from their adult occurrence (Appendix 1).
Therefore, we developed a separate bias file for the E. laidlawiusing all the sampling sites from Dorji (2015) along with occurrence
coordinates from Brockhaus and Hartmann (2008) and Dupchu, S (Personal
communication). We used Hydrosheds (hybas_as_lev12_v1c available inwww.hydrosheds.org, Lehner and
Grill, 2013) clipped to the Bhutan boundary to bound the occurrence
instead of regular sized grid cells of the environmental variables
(Phillips et al. 2009; Syfert et al. 2013) to develop sampling bias
grids.