The Crotolaria species are from the legume family

Crotolaria species (ripe fruits of which are used by children as rattles) are small shrubs bearing bright yellow blooms and are common across the Indian countryside. But Indian botanists have just discovered two rattlepod species — woody and multi-bracted rattlepods — that survive only in the hill tracts of Maharashtra.

Of the 85 species of rattlepods or Crotolaria found in India, 73 survive only in peninsular states. Many of these are concentrated along the Western Ghats and it takes a trained eye to discern the (often) slight physical differences between various rattlepod species. On their field trips to Maharashtra’s Kolhapur district in 2011 and 2015, researchers at the University of Delhi’s Department of Botany spotted two types of rattlepods that looked unlike any they had seen before. Intrigued, they collected specimens and measured in detail the fine morphological features specific to these plants in their lab. They found that the width of the keel (one of the petals of a flower) was different from any of the other rattlepod species seen in the area. “The degree to which the keel is twisted in the flowers also emerged as an important characteristic,” says Arun Pandey, professor at the University of Delhi, who led the study published in PLOS ONE recently.

Two species

To make sure they were looking at two different species, the botanists also analyzed the plants’ DNA and studied portions of two plant genes. Using six samples of the new plants, they built a genetic 'species tree', which shows the plants' genetic affinities with other rattlepod species. This reveals that both the new shrubs are different enough to warrant recognition as separate species.

The team named one species Crotolaria suffruticosa (’suffruticose’ means woody at its base, but herb-like above). This ‘woody’ rattlepod is found in grasslands and forest edges in two localities in Kolhapur’s Karul Ghat. The second, Crotolaria multibracteata (named after its several bracts – small modified leaves at the bases of flowers) or the ‘multi-bracted’ rattlepod survives on rocky and dry surfaces in just one locality in the nearby Panhala region. This limited geographical distribution necessitates that both plants be classified as ‘endangered’ as per the criteria set by the IUCN, write the authors.

“Anthropogenic activities such as clearing and burning of forests and grasslands in the non-protected areas where we found them could threaten their existence,” says Prof. Pandey, adding that conserving these habitats is crucial for the rare shrubs.