January 21, 2020

Of Porcupine Palms and Bears

Image by Bigfish

Needle Palm, Rhapidophyllum hystrix, is an interesting species patchily distributed in the Southeastern U.S. The sole member of the genus, it’s generally found in river floodplains and moist bottomlands. It’s scarce or endangered throughout most of its range. In Florida, where numerous populations occur, it can often be found on moist riverbanks, growing above water-loving Dwarf Palmetto, Sabal minor, and below Saw Palmetto, Serenoa repens, which thrive on higher, drier sites. Of course, “higher” when referring to topography in the Sunshine State, is a subtle descriptor.
Image by Bigfish
Needle Palm develops stubby, clustering trunks; highly dissected palmate leaves arise from stems that are armed with long black spines. 
Unripe fruit
Image by Alan Cressler
Its flowers and musty or foul-smelling fruit are a formidable deterrent to larger creatures that might consume them. It seems that the species isn’t very good at reproducing. 
Male inflorescence
Seedlings tend to germinate too close to the mother plants, thus most don’t thrive. Needle Palm is considered a relictual species, one whose ancestors were more widespread. It’s possible that extinct plant-feeders, such as giant ground sloths, were its primary seed-dispersers. Black Bears currently fill that ecological function.
 Characteristic of Needle Palms in habitat is the quantity of leaf litter that is in the dense spines. Perhaps this trait has evolved primarily to funnel nutrients to the plants’ roots as the debris decomposes.
Seedlings and debris trapped in spines
Image by Bigfish
Maybe physical protection is a secondary effect. The spines don’t stop bears from consuming the ripe fruit; probably Giant Ground Sloths weren’t discouraged, either.  
Giant Ground Sloths were peaceful foragers except when surprised

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