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<p>A specimen-based investigation of South American Ochnaceae surfaced a number of entities with similar morphologically distinctive characters. These distinctive taxa had <i>a priori</i> identifications of <i>Blastemanthus</i> or indeterminate Ochnaceae, but they display an unusual combination of characters that do not match the concepts of <i>Blastemanthus</i> or any other described Ochnaceae taxon. These morphologically distinctive taxa share with <i>Blastemanthus</i> tightly packed parallel secondary leaf veins and lanceo-conical flower buds bearing shingled bud scales. However, all known species of <i>Blastementhus</i> display racemes to stoutly branched thyrses bearing medium-sized staminodal flowers, and woody, thick-walled, subulate capsules with axile placentation and elongated seeds; this is in contrast to these morphologically distinctive taxa that uniformly display multibranched panicles with prominent secondary branches bearing smaller proportioned flowers lacking staminodes, and smaller-sized thin-walled ellipsoid to rounded, inflated capsules with parietal placentation and spherical seeds. To reflect their morphological distinctiveness, these six new species, described within the new genus <Emphasis Type="BoldItalic">Igapodendron</Emphasis> are <Emphasis Type="BoldItalic">Igapodendron amazonica</Emphasis>, <Emphasis Type="BoldItalic">I</Emphasis><b>. </b><Emphasis Type="BoldItalic">aracaense</Emphasis>, <Emphasis Type="BoldItalic">I</Emphasis><b>. </b><Emphasis Type="BoldItalic">cubatense</Emphasis>, <Emphasis Type="BoldItalic">I</Emphasis><b>. </b><Emphasis Type="BoldItalic">curicuriariense</Emphasis>, <Emphasis Type="BoldItalic">I</Emphasis><b>. </b><Emphasis Type="BoldItalic">pasimoniense</Emphasis>, and <Emphasis Type="BoldItalic">I</Emphasis><b>. </b><Emphasis Type="BoldItalic">temiense</Emphasis>, which is further divided into&#xa0;<Emphasis Type="BoldItalic">I</Emphasis><b>.</b><Emphasis Type="BoldItalic"> temiense</Emphasis><b> var. </b><Emphasis Type="BoldItalic">atabapense</Emphasis> and the nominate variety. <i>Igapodendron</i> is restricted to northern Amazonia in Brazil, Colombia, and Venezuela, with its species displaying narrowly endemic ranges correlated to specific river drainages, mostly within the upper and middle Rio Negro drainage basin. The distribution of this new genus and its component species are discussed in the context of South American Ochnaceae biodiversity patterns.</p>

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Igapodendron (Ochnaceae), a new genus with six new species from northern Amazonia

  • 期刊论文

  • 发表日期：

    2026年5月28日

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  • Matthew C. Pace

摘要

A specimen-based investigation of South American Ochnaceae surfaced a number of entities with similar morphologically distinctive characters. These distinctive taxa had a priori identifications of Blastemanthus or indeterminate Ochnaceae, but they display an unusual combination of characters that do not match the concepts of Blastemanthus or any other described Ochnaceae taxon. These morphologically distinctive taxa share with Blastemanthus tightly packed parallel secondary leaf veins and lanceo-conical flower buds bearing shingled bud scales. However, all known species of Blastementhus display racemes to stoutly branched thyrses bearing medium-sized staminodal flowers, and woody, thick-walled, subulate capsules with axile placentation and elongated seeds; this is in contrast to these morphologically distinctive taxa that uniformly display multibranched panicles with prominent secondary branches bearing smaller proportioned flowers lacking staminodes, and smaller-sized thin-walled ellipsoid to rounded, inflated capsules with parietal placentation and spherical seeds. To reflect their morphological distinctiveness, these six new species, described within the new genus Igapodendron are Igapodendron amazonica, I. aracaense, I. cubatense, I. curicuriariense, I. pasimoniense, and I. temiense, which is further divided into I. temiense var. atabapense and the nominate variety. Igapodendron is restricted to northern Amazonia in Brazil, Colombia, and Venezuela, with its species displaying narrowly endemic ranges correlated to specific river drainages, mostly within the upper and middle Rio Negro drainage basin. The distribution of this new genus and its component species are discussed in the context of South American Ochnaceae biodiversity patterns.