A mountain range in southwestern Haiti is an underappreciated cradle of plant diversity. A study in the Botanical Journal of the Linnean Society has found that the region spawned many unique plant species, and also, revealed the flight paths of the birds that kickstarted this evolutionary spurt.
The Caribbean islands are one of the world’s 36 recognised hotspots for plant biodiversity. Within that, a third of the plant species in Hispaniola (the island containing Haiti and the Dominican Republic) are endemic - found there and nowhere else. Within that, the Massif de la Hotte mountains contain an unusually high concentration of endemic species. “It’s a biodiversity hotspot within a biodiversity hotspot,” says Andrew Naranjo from Florida International University.
So, the question is, why does this small mountain chain contain more plant diversity than just about any other spot in the Caribbean? To find out, Naranjo and colleagues studied Hispaniola’s melastomes, tropical plants with seeds that are mainly dispersed by birds.
Hispaniola contains 130 endemic species of melastome. By studying the DNA of these plants, alongside historical data, the team created a family tree that showed when and where different species evolved.
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Many of the ancestors of today’s melastomes came from Cuba. Millions of years ago, the plants were carried to the Massif de la Hotte in the bellies of the birds that ate their fruits, then flew to Haiti. There, the excreted seeds sprouted and over time, the plants diversified to form new species. This happened at least 19 times, including one occasion where the original species evolved to produce 18 new ones.
The bird that carried this particular seed made its 100-kilometre journey 1.6 million years ago, so the study doesn’t just tell us about plant biodiversity, it also tells us about the ancestral flight paths of these birds.
There were other routes too. The study reveals various ancient and erratic flight paths fanning out in all directions across the Caribbean, including from Hispaniola and Cuba to Jamaica and Puerto Rico, and from Cuba to the Lesser Antilles.
Now, climate change and deforestation are threatening the plants of the Massif de la Hotte. Most of the melastomes there live at elevations above a kilometre. As the world warms, they are increasingly stuck between rock and empty sky. “They can’t go anywhere else,” says Lucas Majure from the Florida Museum of Natural History. So, the team hope their findings will help the plants’ conservation.
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Top image: Massif de la Hotte in Haiti. Credit: Lucas Majure
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