Scientists trace ancient bird flight paths using modern plant diversity

The Massif de la Hotte is a young, exceptionally biodiverse mountain range in southern Haiti that is home to an unusually large number of species that grow there and nowhere else.
Scientists used a group of plants called melastomes as a case study to determine how, when and why this mountain range accumulated so many unique species.
The results suggest that birds flying over the Caribbean Sea between eastern Cuba and southwest Hispaniola may be responsible for a significant proportion of the region’s diversity.
The study builds on decades of research, most notably that of the botanists Erik Ekman and Walter Judd.

It’s not what they intended to do or expected to find. They’re not even all that interested in birds. When Andre Naranjo and his colleagues began work on a new study published in the Botanical Journal of the Linnean Society, they wanted to know why a small mountain chain on the island of Hispaniola had more plant diversity than just about any other spot in the Caribbean. As far as they were concerned, the island’s birds were merely an unnecessarily complicated form of seed dispersal.

Birds made things particularly complicated in this case, because according to their results, a significant portion of the plant diversity on the Massif de la Hotte in southern Hispaniola didn’t come from other parts of the island, as they’d expected. Instead, they seem to have originated in eastern Cuba, suggesting that birds regularly traveled between the islands along a specific route. The authors say that other modes of dispersal cannot be ruled out, but because birds commonly consume the fruits produced by many of the plants in question, they are considered the likeliest means of conveyance.

As an example, the authors share their discovery of a dispersal event that occurred 1.6 million years ago when a plucky bird made the non-stop flight of more than 100 miles from southern Cuba to the mountainous Tiburon Peninsula, oriented latitudinally at the southwestern edge of Hispaniola. The bird wisely carbo-loaded before making the trip by eating the sugary fruit of Miconia, a type of flowering plant with deeply grooved leaves and conveniently beak-sized berries. The bird indelicately deposited what remained of the fruit in a white blob of uric acid and undigested cellulose surrounding a perfectly undamaged Miconia seed, which proceeded to sprout into a new plant.

Between then and now, that single, isolated plant evolved into 18 species, most of which can be found on the Massif de la Hotte and nowhere else. Nor are they alone. About 34% of Hispaniola’s plant species are endemic, many of them restricted to this one mountain range.

“It’s a biodiversity hotspot within a biodiversity hotspot,” said the study’s lead author Andre Naranjo, who conducted the research while working as a postdoctoral associate at the Florida Museum of Natural History.

The Caribbean Islands are collectively one of 36 biodiversity hotspots worldwide, defined as an area that harbors at least 1,500 endemic plant species that have been endangered by extensive habitat loss. The Massif de la Hotte is located in the Pic Macaya National Park, which according to Naranjo has lost 75% of its forests despite being one of the oldest national parks in the Caribbean.

“Within the last 35 years, whole habitats have been clear cut by people in the surrounding villages for firewood to literally just survive because the economic situation in Haiti is so dire,” he said.