Epiphytic Habit and Spatial Distribution Patterns of Phalaenopsis deliciosa and Phalaenopsis hainanensis

Epiphytic orchids are the largest group of epiphytes and are important components of forest species diversity. Epiphytic orchids show host preferences. Their spatial distribution is shaped by microhabitat preferences, host tree characteristics, and mycorrhizal associations. In this study, the habitat community structure and epiphytic habits of epiphytic orchids, Phalaenopsis deliciosa and Phalaenopsis hainanensis, distributed on Hainan Island were investigated. The results show that the vascular plant genera in the communities of P. deliciosa and P. hainanensis are characterized by biogeographical affinities dominated by tropical Asian and pantropical elements, accounting for 30.60% and 21.64% in the P. deliciosa community and 26.42% and 24.53% in the P. hainanensis community, respectively. Within the surveyed plots of this study, 41 epiphytic host species were recorded for P. deliciosa and 17 for P. hainanensis. Both P. deliciosa and P. hainanensis showed a high epiphytic preference for Streblus ilicifolius, with selectivity index values of 21.89 and 26.00, respectively. Both P. deliciosa and P. hainanensis exhibited clear small-scale aggregated horizontal distributions, with the O-ring analysis indicating statistically significant clustering (p < 0.05). Specifically, P. hainanensis showed aggregation within the 0.25–0.75 m range, whereas P. deliciosa displayed aggregation at radii of 0.25–2.25 m. In the vertical distribution, individuals of P. deliciosa occurred below 5 m and were concentrated at heights of 1–1.9 m. Individuals of P. hainanensis were distributed below 4 m, with no significant differences among height classes, although the highest abundances occurred at heights of 0–0.9 m and 2–2.9 m. Heights of 0–0.9 m and 2–2.9 m were the most abundant. In summary, individuals of both Phalaenopsis species were predominantly distributed at lower height ranges. The protection of the habitat plant community, especially the preferred epiphytic tree species or companion plants, should be strengthened to conserve the Phalaenopsis species.