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Table 2 Relative abundance of parental species in the contact zone and the direction of hybridization in 6 cases from 4 genera

From: Testing a hypothesis of unidirectional hybridization in plants: Observations on Sonneratia, Bruguiera and Ligularia

Hybrid (Location) Relative abundance of parental species Direction of hybridization
Sonneratia × gulngai (Qionghai, Hainan)
(Wenchang, Hainan)
S. alba: S. caseolaris ~1:1 (71:97; 664:573)
~1:1 (83:112; 556:477)
(equally common)
S. × hainanensis (Wenchang, Hainan) S. alba: S. ovata ~10:1 (340:37) C♀ × R♂
Bruguiera × rhynchopetala (Haikou, Hainan) B. sexangula: B. gymnorrhiza ~2:1 (98:53) C♀ × R♂ (29)
R♀ × C♂ (5)
Ligularia paradoxa × duciformis (Maoniushan, Yunnan) L. paradoxa: L. duciformis ~5:1 C♀ × R♂
Rhizophora × annamalayana (West coast, Sri Lanka) R. mucronata: R. apiculata ~100:1 C♀ × R♂
R. × lamarkii (Daintree River and Shoalwater Bay, Australia) R. stylosa: R. apiculata ~100:1 C♀ × R♂
  1. Note: For Sonneratia × gulngai, the hybrid zones both in Qionghai and in Wenchang are about 1 km long. We recorded the number of individuals of the parental species both within the zone of hybridization (the former) and in the neighboring 3 km-long zone (the latter). The latter zone is composed solely of parental species. For S. × hainanensis, we counted the number of individuals of S. alba only around the range of S. ovata and S. × hainanensis. Other cases are restricted the exact zones of hybridization.