Identifying juveniles changes our interpretation of similarities among communities
The Mantel test revealed that there are substantial differences in the species compositions of communities when considering only adult specimens or individuals of all life stages, and the ANOSIM showed that taking immature specimens into account reduced the differences in species composition between communities at different latitudes. The NMDS plots also revealed differences in community similarities between the two approaches. While in the NMDS with only adults most communities were more similar to other communities within the same park than to communities from different parks, this pattern was much less pronounced in the NMDS that includes juveniles. In addition, the marked distinction between communities at higher latitudes and communities at lower latitudes found with adults only was not recovered when considering all the individuals. This lower structure in the NMDS based on specimens of all life stages suggests that phenological differences among communities may lead to see community compositions as more different than what they really are. In the time of the sampling, a species might be present as adult in a certain community and still as juvenile in another community, so by taking into account exclusively adult stages we might be inadvertently accentuating the differences among community compositions.
Given that seasonality and marked phenologies with different life stages present at different times of the year are very common across many animal groups (Scott & Epstein, 1987; Jakob, Poizat, Veith, Seitz, & Crivelli, 2003; Lazaridou-Dimitriadou & Sgardelis, 1997), we suspect that the phenomenon that we describe here might also apply to inventories performed with other organisms. Studies on other animal taxa comparing alpha diversity estimates of a community using only individuals of a certain life stage or all individuals might help reveal if this trend is constant across different taxa.