The Lepanthes nummularia complex

 

Introduction

       A distinctive group of small pendant chainlike Lepanthes species forms the subgenus Brachycladium Luer. Members of this subgenus occur in the Andes mostly at middle elevations (1700-2500 m in eastern Ecuador) in very wet ridgetop forests, where they are usually rare and local. They are seldom noticed or collected by nonspecialists because of their inconspicuous leaves barely larger than the moss in which they grow, but they are extremely diverse and there are new species discovered every year. The most common species is L. nummularia Rchb.f, which occurs from Colombia to Peru. Dr. Luer (1994) notes that L. nummularia is very variable: "Some populations with small, elliptical leaves five millimeters long and three millimeters wide contrast with others with orbicular leaves 12 millimeters long and 11 millimeters wide...No two lips from different collections are exactly the same. The same is true with the column. In some specimens the column is thick, terete and more or less clavate. In other collections the column is more or less flattened and dilated near the middle".

 

All these forms of L. nummularia were found in a single spot in the Tapichalaca Reserve of southern Ecuador. One other form, not in this illustration, was also found there.

 

     During my studies of the orchid flora of particular east Andean sites, I have been finding evidence which strongly suggests that there are several species currently lumped into L. nummularia. Four of these are sympatric in the wet forest of the Tapichalaca Reserve, owned by the Jocotoco Foundation and located between Yangana and Valladolid in Zamora-Chinchipe Province, Ecuador. It is this sympatry which proves that they are not simply geographic races of L. nummularia. In this forest some of the forms are common enough that I could assess their variability. I found no evidence of crossbreeding between any of these forms, even though they all grow intermixed on the same trees. Therefore I propose to split these Tapichalaca forms into four different species. Until I have figured out which one (if any) is the real L. nummularia as described from Jameson's 1856 collection near Quito, I shall refer to them as A, B, C, and D. Forms A and B are the common ones. The photographs that follow illustrate the differences. Note that these eight photos are all from Tapichalaca, and all were taken and reproduced at the same scale so that size differences in the images reflect real differences in flower sizes.

 

Form A
Form B
Form C
Form D
Lateral views. Note lip and column differences. All photos are at the same scale so differences in sizes are real.

 

    Form A is the big-leaved form mentioned in Dr. Luer's quotation above. All specimens examined (n = about 10) are much larger than the plants of the other Tapichalaca forms, and all have a thick column with a large appressed lip. Form B has tiny flowers that resemble the flowers of A but smaller, with much longer lower lobes of the petals and a much more slender column. The lip curves downward before curving forward. This is the most common form at Tapichalaca. Examples vary slightly in the size and shape of the petals, but show little or no variation in the column or lip. Form C has tiny petals but a thick column like A. The lip, however, is microscopic. I found two of these. Form D is much like Form B but has a thinner column with a disproportionately long anther, and is the most distinctive of these forms. I found only one of these in Tapichalaca, but I have seen the same form in other places.

 

   Because all these forms grow together without interbreeding (as evidenced by the lack of intergradation at Tapichalaca) I think that these are all good species in spite of their similarities. The problems begin when I examine collections from outside the Tapichalaca area. We may safely assume that all four of these species are geographically variable. Many of the collections from outside Tapichalaca do not exactly match any of the Tapichalaca forms, but may still be geographic variations of those forms. This is where we need the extra clues that DNA analysis can provide about relationships. Dr. Mark Wilson and his students will be doing this DNA analysis soon. Meanwhile we can make some tentative conclusions based in morphology.

 

Let's look at the different L. numularia forms as we move northward from Tapichalaca. These will open in their own browser windows so you can compare them side by side:

Paute-Mendez Road (230 km N of Tapichalaca)

Banos (370 km N of Tapichalaca)

Sumaco-Galeras National Park (460 km N of Tapichalaca)

La Bonita, near Colombian border (550 km N of Tapichalaca)

Forms from Los Cedros, in the western Andes (530 km N of Tapichalaca)

Conclusions

 

Literature Cited:

Luer, Carl. 1994. Icones Pleurothallidinarum XI: Systematics of Lepanthes Subgenus Brachycladium and Pleurothallis Subgenus Aenigma, Subgenus Elongatia, Subgenus Kraenzlinella. Monogr. Syst. Bot. 52. St. Louis, Missouri.

 

 

The Lepanthes nummularia complex