Results
DNA-based species delimitations. In Panama we surveyed 90 trees over three rounds of sampling, representing 53 species, 48 genera, and 29 families. We found live diaspidids on 75 trees, yielding 380 female specimens (adults and second instars). At least two loci were successfully amplified for 184 specimens, belonging to 53 DNA-delimited species (Fig. A1.6; Table A1.1). Assignment to a morphologically defined species was possible for 180 specimens, representing 32 described and 12 undescribed species. Species assignments and trophic links are in Table S2. In Malaysia, we surveyed 211 trees over 20 rounds of sampling, including 85 species, 48 genera, and 27 families. We found live diaspidids on 102 trees, yielding 480 female specimens. At least two loci were successfully amplified for 266 specimens, belonging to 123 DNA-delimited species (Fig. A1.7 Table A1.1). Assignment to a morphologically defined species was possible for 259 specimens, representing 20 described and 58 undescribed species. Species assignments and trophic links are in Table S3.
We found strong evidence for host-use specialization, both in terms of less-than-expected host plant diversity, and more-than-expected phylogenetic conservatism of host use. The Simpson’s RDI of each diaspidid species’ diet was significantly lower than expected at all host taxonomic levels and in both locations, except at the host-species level in Panama (Table A1.2). Phylogenetic signal was significantly stronger than its null expectation for 19 host taxa (Figure A1.8), although it was higher at the Malaysia site (mean 0.61) than the Panama site (mean 0.45), with 18 Malaysian host taxa with significant phylogenetic conservatism, compared to just one Panamanian host taxon with significant conservatism.
Despite the prevalence of diaspidid host-use specialization at our two sites, and of extensive phylogenetic conservatism of host use in Malaysia, we found no evidence for performance trade-offs on alternative hosts that would select against broad diets. Specialists were no more abundant than generalists on specific host trees; the number of live adult or second instar female diaspidids found on each tree was not correlated with diet breadth (Fig. 1; Table A1.4). Moreover, contra the metapopulation trade-off hypothesis, diaspidids with broader diets were observed on a higher proportion of the trees in their host taxa, although this effect was not significant for Malaysian diaspidids and their host plant species (Figure 2; Table A1.4).
Morphology-based delimitations. The results of the analyses using morphologically delimited species were broadly consistent with those using DNA-delimited species. As for analyses using DNA-delimited species, with morphology-delimited species we found that diaspidid species were more specialized than expected by chance (Table A1.3), that more specialized species were no more abundant on their hosts (Table A1.5), and tended to occupy a smaller proportion of their potential host plants (Table A1.5). Actually, when modelling the links between Malaysian diaspidids and their hosts at the species level, we found positive effect of diet breadth on abundance that fell just short of significance (p-value = 0.08).