Long-Distance Dispersal by Sea-Drifted Seeds Has Maintained the Global Distribution of Ipomoea pes-caprae subsp. brasiliensis (Convolvulaceae)

Abstract

Ipomoea pes-caprae (Convolvulaceae), a pantropical plant with sea-drifted seeds, is found globally in the littoral areas of tropical and subtropical regions. Unusual long-distance seed dispersal has been believed to be responsible for its extraordinarily wide distribution; however, the actual level of inter-population migration has never been studied. To clarify the level of migration among populations of I. pes-caprae across its range, we investigated nucleotide sequence variations by using seven low-copy nuclear markers and 272 samples collected from 34 populations that cover the range of the species. We applied coalescent-based approaches using Bayesian and maximum likelihood methods to assess migration rates, direction of migration, and genetic diversity among five regional populations. Our results showed a high number of migrants among the regional populations of I. pes-caprae subsp. brasiliensis, which suggests that migration among distant populations was maintained by long-distance seed dispersal across its global range. These results also provide strong evidence for recent trans-oceanic seed dispersal by ocean currents in all three oceanic regions. We also found migration crossing the American continents. Although this is an apparent land barrier for sea-dispersal, migration between populations of the East Pacific and West Atlantic regions was high, perhaps because of trans-isthmus migration via pollen dispersal. Therefore, the migration and gene flow among populations across the vast range of I. pes-caprae is maintained not only by seed dispersal by sea-drifted seeds, but also by pollen flow over the American continents. On the other hand, populations of subsp. pes-caprae that are restricted to only the northern part of the Indian Ocean region were highly differentiated from subsp. brasiliensis. Cryptic barriers that prevented migration by sea dispersal between the ranges of the two subspecies and/or historical differentiation that caused local adaptation to different environmental factors in each region could explain the genetic differentiation between the subspecies.

Navigating the ‘broad freeway’: ocean currents and inland isolation drive diversification in the Pandanus tectorius complex (Pandanaceae)

“…Compared with the two previous studies investigating geographical patterns in the similarly distributed H. tiliaceus and I. pes‐caprae , (Takayama et al ., ; Miryeganeh et al ., ), much greater geographical differentiation was found in the P. tectorius complex. This is likely due to differences in the frequency of migration, which is influenced by the length of time that fruits can remain afloat with viable seeds.…”

Genetic Structure and Population Demographic History of a Widespread Mangrove Plant Xylocarpus granatum J. Koenig across the Indo-West Pacific Region

“…brasiliensis (L.) van Ooststr. [52] and the genus Rhizophora [10]. However, topographic barriers can act as genetic barriers even in these species.…”

Vegetational changes in the coral-gravelly barrier spit appearing after the 2004 Indian Ocean Tsunami at Pakarang Cape, southwestern Thailand, related to topographical changes

“…Plant communities found on the barrier spit of Pakarang Cape were fundamentally composed of pantropical plants with sea-drifting seeds (Miryeganeh et al 2014). Almost all species are common in tropical coasts and were also found on neighboring Phuket Island (Hayasaka et (Backer 1929, Tagawa 1989, where the occurrence of the most common 19 species took 23 years after the 1883 catastrophic eruption.…”