Spintharus flavidus

Hentz, 1850

Spintharus flavidus is a cobweb in the Theridiidae, historically considered a single widespread ranging from northern North America to Brazil and throughout the Caribbean. Molecular phylogenetic analysis has rejected this hypothesis, revealing instead a 30 million year old radiation of at least 16 distinct species in the Caribbean region alone. Nearly all are short-range with limited overwater ability. The Caribbean event occurred approximately 30 million years ago, coinciding with the GAARLandia landbridge hypothesis.

Spintharus flavidus by (c) Judy Gallagher, some rights reserved (CC BY). Used under a CC-BY license.

Common Spiders U.S. 302 Spintharus flavidus by James Henry Emerton (1847 – 1931). Used under a Public domain license.

Arachtober 25 -3 - Spintharus flavidus, Prince William Forest Park, Triangle, Virginia (24070644598) by Judy Gallagher. Used under a CC BY 2.0 license.

Pronunciation

How to pronounce Spintharus flavidus: /spɪnˈθɑːrəs ˈflævɪdəs/

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Identification

Molecular data are required to distinguish the cryptic within this complex; morphological identification alone is unreliable given the historical lumping of multiple species under this name. The Spintharus is old, with its sister lineage Episinus documented in 45 million year old Baltic amber.

Images

Habitat

Occupies cryptic in leaf litter or on undersides of low-level leaves.

Distribution

Historically reported from northern North America to Bolivia, Brazil, and throughout the Caribbean. Molecular evidence indicates this range comprises a radiation of distinct : at least 16 in the Caribbean (nearly all short-range or single island endemics), with additional distinct mainland groups in North, Central, and South America. GBIF records confirm presence in Trinidad and the USA, with Brazilian records from Amazonas, Pará, and Rio Grande do Sul.

Behavior

ability is limited. A single documented instance of ballooning (aerial dispersal on threads) has been observed, but the dispersal distance was short; long-distance overwater dispersal appears rare despite this capability.

Similar Taxa

SpintharusThe contains only two described , with S. flavidus historically encompassing what molecular data now reveal to be at least 16 distinct Caribbean species plus mainland lineages. The other described species in the genus has not been subject to similar molecular revision.

Misconceptions

The primary misconception is that S. flavidus represents a single widespread capable of frequent overwater . Molecular phylogenetic analysis of three loci (COI, 16S, ITS2) from 195 individuals rejects this hypothesis, demonstrating instead that the name has been applied to a diverse radiation of short-range species with limited dispersal ability.