Wednesday, February 15, 2017

[Botany • 2017] Impatiens tanintharyiensis • A New Species (Balsaminaceae) from Southern Myanmar

Impatiens tanintharyiensis  Ruchisansakun, Suksathan & Saw-Lwin 


Impatiens tanintharyiensis Ruchisansakun, Suksathan & Saw-Lwin from the Tanintharyi region of Southern Myanmar is described and illustrated as a new species. The presence of connate lateral united petals and a four-locular ovary, as well as results of molecular phylogenetic analyses of nuclear ITS and plastid atpB-rbcL spacer DNA sequences, suggest that the new species is a member of Impatiens section Semeiocardium (Zoll.) S.X. Yu & Wei Wang. The new species is morphologically most similar to I. spectabilis Triboun & Suksathan, but can be distinguished by its asymmetric flowers, saccate-bucciniform lower sepal, and shorter, slightly incurved spur. Floral traits, including the presence of a large floral chamber with a wide entrance, are consistent with the bee-pollination syndrome in Impatiens. Since I. tanintharyiensis is only known from two small populations, its conservation status is assessed as Endangered.

Keywords: floral asymmetry, Impatiens, lithophyte, Myanmar, Semeiocardium, taxonomy, Eudicots

Impatiens tanintharyiensis  Ruchisansakun, Suksathan & Saw-Lwin

Impatiens tanintharyiensis Ruchisansakun, Suksathan & Saw-Lwin is morphologically similar to I. spectabilis Triboun & Suksathan but can be distinguished by having asymmetric flowers due to anticlockwise distorted lateral united petals, a saccate-bucciniform lower sepal, and a shorter, slightly incurved spur. 

Type:— MYANMAR. Tanintharyi Region: Dawei, Thet Kal Kwet Village. ...

Distribution:— Endemic to Southern Myanmar (Tanintharyi Region), only known from two localities.
Ecology:— Growing among decaying organic material on low granular metamorphic rock of granitic schist facies (Phongphat Prasong, pers. comm), along a waterfall at 146–155 m above sea level.

Etymology:— The specific epithet refers to its locality, the Tanintharyi region of Myanmar.
Common name:— Tanintharyi Dan Pan, Tanintharyi balsam. 

Pollination ecology:— A recent comparative study of floral morphology and pollination ecology demonstrated that the closely related and morphologically similar I. daraneenae, is pollinated by bees (Ruchisansakun et al. 2016). The presence of a large floral chamber with a wide entrance are traits associated with bee pollination in Southeast Asian Impatiens (Ruchisansakun et al. 2016). Based on the traits of the new species, we hypothesize that the new species is also bee-pollinated.

Saroj Ruchisansakun, Piyakaset Suksathan, Timotheüs van der Niet, Saw Lwin and Steven B. Janssens. 2017.  Impatiens tanintharyiensis (Balsaminaceae), A New Species from Southern Myanmar. Phytotaxa.  296(2); 171–179. DOI:  10.11646/phytotaxa.296.2.6

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