04, Table 5). Habitat specialists of small GR were far more likely to have an outcrossing mating system VS-4718 compared to habitat specialists of large GR (ratio 16:1, Fig. 3). Fig. 3 Frequency distribution of mating systems between habitat generalist and habitat specialist species of small GR. Habitat specialists are more likely to have an outcrossing mating system (Fisher’s exact test, P = 0.04) Table 5 Results of logistic regression for pollination, dispersal, and mating system Source Nparm DF χ2 Prob > χ2 Pollination GR 1 1 0.656 0.418 LA 1 1 0.102 0.749 GR*LA 1 1 1.510 0.219 GR 1 1 1.599
0.206 HS 1 1 CA4P purchase 2.248 0.134 GR*HS 1 1 0.016 0.899 Dispersal GR 1 1 1.312 0.252
LA 1 1 2.037 0.154 GR*LA 1 1 2.037 0.154 GR 1 1 2.703 0.100 HS 1 1 0.442 0.506 GR*HS 1 1 0.237 0.627 Mating system GR 2 2 3.045 0.218 LA 2 2 4.534 0.104 GR*LA 2 2 0.511 0.775 GR 2 2 2.076 0.354 HS 2 2 0.420 0.811 GR*HS 2 2 6.468 0.039 Two models were performed for each dependent variable as HS and LA were correlated and could not be included in the same analysis. Significant P-values (below 0.05) are in bold Discussion Species with small GRs were more likely to have abiotic, rather than biotic, seed dispersal mechanisms. Results for the other two rarity axes were inconclusive. This was likely due to the non-independence between HS and LA in our dataset and our small sample sizes. Seed dispersal SBE-��-CD mouse by gravity is common among plants. It is intuitive that gravity dispersal would lead to small GRs. In this case seed dispersal by gravity may very cause this type of rarity rather than be a consequence of it. Water-dispersed species of small GRs are logistically unlikely, although at least one species of mangrove has both these characteristics (Kruckeberg and Rabinowitz 1985). Ant- and ballistic/gravity-dispersed seeds are rarely moved thousands of meters, thus species with these particular dispersal agents are unlikely to have large GRs.
The significant interaction between HS and GR for mating system showed that habitat specialists of small GR are far more likely to have outcrossing mating systems than habitat specialists of large GR. Other studies have found that rarity is associated with higher degrees of self-incompatibility (Kunin and Gaston 1993 and references therein). Greater outcrossing rates leads to greater effective population sizes within populations (Heywood 1986). An outcrossing mating system, therefore, buffers habitat specialists of small GR against genetic drift. Because of the high degree of outcrossing, we then might have expected that habitat specialists of small GR might have had a greater prevalence of insect pollinated species.