Sunday, November 18, 2012

Is Lantana depressa Sphingophilous?

Lantana depressa

Lantana depressa is a dwarf, evergreen, short-lived shrub that bears small but numerous bright yellow flowers. It is a state-listed endangered species that occurs only in Miami-Dade County. The flowers are attractive to butterflies and it is sometimes grown as a nectar plant in butterfly gardens.

On Tuesday, November 6, 2012, at approximately 5:30 PM (Eastern Daylight Saving Time) I was at the local Home Depot and noticed a large, brown sphinx moth repeatedly and persistently visiting the flowers of Lantana depressa. I purchased two plants and, after getting them home, I noticed for the first time that the flowers were fragrant. The fragrance was not powerful but it was distinct and clearly noticeable. It was sweet and pleasant but was unlike any other floral scent I have ever experienced. The next day, I tested the flowers to see if they were fragrant during the day but the scent was almost undetectable.

Based on these observations, it appears that Lantana depressa employs a dual pollinating strategy: psychophily (butterfly pollination) during the day and sphingophily (sphinx moth pollination) during the night. The presence of a distinct sweet odor that intensifies at night is a classic sign of sphinx moth pollination. Also, an adaption to sphinx moths as pollinators might explain an important distinction between Lantana depressa and the weedy, non-native, and invasive Lantana camara. The latter has flowers that open up one color and then fade to another. This allows pollinators to readily distinguish fresh, nectar-filled flowers from older flowers as well as creating a more easily noticeable floral display. In Lantana depressa, older flowers do not change color or else become merely a slightly darker shade of yellow. If Lantana depressa is transitioning to or has become adapted to sphinx moth pollination, this would explain the color constancy of the flowers since a difference in color between new and older flowers would not be perceptible to nocturnal sphinx moths.

Before ending this post, I would like to point out another interesting observation made at the Home Depot on November 6. Growing immediately adjacent to the pots of Lantana depressa were numerous cultivars of Lantana camara. The latter bore innumerable fruits in all stages of maturity whereas not a single fruit was to be seen on the plants of Lantana depressa. Although Lantana depressa will cross-breed with, and be genetically swamped by, Lantana camara, it appears as if that particular Home Depot clone of Lantana depressa was both self-sterile and not interfertile with the adjacent clones of Lantana camara.

Image and text © 2012 Rufino Osorio

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