Xylaria species associated with fallen leaves and petioles.

Background: Xylaria species growing on fallen leaves and petioles have not been treated systematically. One source of confusion in this group of Xylaria species has stemmed from X. filiformis, which is an ancient name published in 1805 as Sphaeria filiformis and has commonly labeled on specimen packets that contain leaf- and petiole-inhabiting Xylaria species. Here we clarified the identity of X. filiformis and distinguish it from the species that are easily confused with it, notably X. simplicissima, to which most specimens labeled as X. filiformis are referred. Our research also led us to encounter many other leaf- and petiole-inhabiting Xylaria species, prompting a comprehensive study of this group of fungi.

Results: Forty-five foliicolous and caulicolous species of Xylaria were studied, including nine newly described species-X. allima, X. appendiculatoides, X. hispidipes, X. minuscula, X. neblinensis, X. spiculaticlavata, X. vermiformis, X. vittatipiliformis, and X. vittiformis; three unnamed species-X. sp. AR1741, X. sp. GS7461A, and X. sp. GS7461B; X. simplicissima, a name newly combined with Xylaria from Rhizomorpha simplicissima; and X. noduliformis and X. imminuta, which are two new replacement names, respectively, for X. maitlandii var. nuda and X. hypsipoda var. microspora. The 45 taxa can be classified into three groups by stromatal shape and conspicuousness of perithecial mounds on the stromatal surface: (i) the X. filiformis group contains 10 species, (ii) the X. phyllocharis group contains 19 species, and (iii) the X. heloidea group contains 16 species. One of the newly described or unnamed species belongs to the X. filiformis group-X. vermiformis; nine of them belong to the X. phyllocharis group-X. allima, X. appendiculatoides, Xylaria minuscula, X. neblinensis, X. sp. AR1741, X. sp. GS7461B, X. spiculaticlavata, X. vittatipiliformis, and X. vittiformis; and three of them belong to the X. heloidea group-X. hispidipes, X. imminuta, and X. sp. GS7461A.

Conclusion: The 45 species of Xylaria associated with fallen leaves and petioles can be identified by using the dichotomous identification key that we provided herein. It is important to note that most of the studied species are represented by only one or several specimens and many have not been recollected and cultured.