Harvestman phylogeny

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Phylogenetic analysis by Garwood et al. (2014) showing the diversification of Opiliones

Harvestmen (

monophyletic
, that is share a common ancestor, others are not, and the relationships between families are often not well understood.

Position in Arachnida

The relationship of harvestmen with other arachnid orders is still not sufficiently resolved.

Scorpiones

Opiliones

Pseudoscorpiones

Solifugae

Dromopoda
(after Giribet et al. 2002)[1]

Opiliones

Scorpiones

Pseudoscorpiones

Solifugae

Dromopoda
(after Shultz 1990)[2]

Up until the 1980s they were thought to be closely related to mites (

Novogenuata.[2] An analysis also considering fossile taxa[1] concluded that the harvestmen are sister to Haplocnemata (Pseudoscorpions and Solifugae), with Scorpions being the sister group of those three combined.[3] Recent analyses have also recovered the Opiliones as sister-group to the extinct Phalangiotarbids,[4][5] although this has low support, or as sister group to a pseudoscorpion and scorpion clade.[6][7]

Relationship of suborders

In 1796,

Tord Tamerlan Teodor Thorell (1892) recognized the suborders Palpatores, Laniatores, Cyphophthalmi (called Anepignathi), but also included the Ricinulei as a harvestman suborder. The latter were removed from the Opiliones by Hansen and William Sørensen
(1904), rendering the harvestmen monophyletic.

Cyphophthalmi

Eupnoi

Dyspnoi

Laniatores

(after Giribet et al. 2002)[1]

Cyphophthalmi

Eupnoi

Dyspnoi

Laniatores

(after Shultz 1998)[8]

According to more recent theories, Cyphophthalmi, the most basal suborder, are a sister group to all other harvestmen, which are according to this system called Phalangida. The Phalangida consist of three suborders, the Eupnoi, Dyspnoi and Laniatores. While these three are each monophyletic, it is not clear how exactly they are related. In 2002, Giribet et al. came to the conclusion that Dyspnoi and Laniatores are sister groups, and called them Dyspnolaniatores, which are sister to Eupnoi.[1] This is in contrast to the classical hypothesis that Dyspnoi and Eupnoi form a clade called Palpatores.[3] Dyspnolaniatores was also recovered in a 2011 study.[9]

In 2014, new analysis by Garwood et al. examined 158 morphological traits across 272 species. In Garwood's

Ordivician.[10]

Genetic analysis performed on a modern Phalangium opilio specimen found that a suppressed gene that, if active, would generate a second pair of eyes at the lateral location, providing independent evidence of four eyes being the ancestral condition. Garwood et al. also argue that Carboniferous harvestmen diversification is more consistent with changes observed in other terrestrial arthropods, which have been linked to high oxygen levels during that period.[10]

Relationship within suborders

Phylogenetic analyses of Opiliones

Cyphophthalmi

The Cyphophthalmi have been divided into two infraorders,

Stylocelloidea and its single family Stylocellidae, and Ogoveoidea, including Ogoveidae and Neogoveidae
); however, recent studies suggest that the Sironidae, Neogoveidae and Ogoveidae are not monophyletic, while the Pettalidae and Stylocellidae are. The division into Temperophthalmi and Tropicophthalmi is not supported, with Troglosironidae and Neogoveidae probably forming a monophyletic group. The Pettalidae are possibly the sister group to all other Cyphophthalmi.

While most Cyphophthalmi are blind, eyes do occur in several groups. Many Stylocellidae, and some Pettalidae bear eyes near or at the base of the ozophores, as opposed to most harvestmen, which have eyes located on top. The eyes of Stylocellidae could have evolved from the lateral eyes of other arachnids, which have been lost in all other harvestmen. Regardless of their origin, it is thought that eyes were lost several times in Cyphophthalmi.

Spermatophores, which normally do not occur in harvestmen, but in several other arachnids, are present in some Sironidae and Stylocellidae.[3]

Eupnoi

male Phalangium opilio

The Eupnoi are divided into two superfamilies, the

Caddoidea and Phalangioidea. The Phalangioidea are assumed to be monophyletic, although only the families Phalangiidae and Sclerosomatidae have been studied; the Caddoidea have not been studied at all in this regard. The limits of families and subfamilies in Eupnoi are uncertain in many cases, and are in urgent need of further study.[3]

Dyspnoi

Troguloidea

Nipponopsalididae

Nemastomatidae

Dicranolasmatidae

Trogulidae

(after Giribet & Kury 2007)[3]
Sabacon cavicolens (Sabaconidae)

The Dyspnoi are probably the best studied harvestman group regarding phylogeny. They are clearly monophyletic, and divided into two superfamilies. The relationship of the superfamily

Sabaconidae, has been investigated in detail. It is not clear whether Ceratolasmatidae and Sabaconidae are each monophyletic, as the ceratolasmatid Hesperonemastoma groups with the sabaconid Taracus in molecular analyses. All other families are grouped under Troguloidea.[3]

Laniatores

Fumontana deprehendor
(Triaenonychidae)

There is not yet a proposed phylogeny for the whole group of Laniatores, although some families have been researched in this regard. The Laniatores are divided into two infraorders, the "

Pentanychidae
, which reside in Travunioidea, could be the sister group to all other Laniatores.

The Grassatores are traditionally divided into the

Oncopodidae may not form a monophyletic group, thus rendering the Phalangodoidea obsolete. The families of the obsolete Assamioidea have been moved to other groups: Assamiidae and Stygnopsidae are now Gonyleptoidea, Epedanidae reside within their own superfamily Epedanoidea, and the "Pyramidopidae" are possibly related to Phalangodidae.[3]

References

  1. ^
    S2CID 16833833
    .
  2. ^
    S2CID 85410687
    .
  3. ^
    ISBN 978-0-674-02343-7
    .
  4. PMID 25405073
    .
  5. PMID 27030415
    .
  6. S2CID 4239867
    .
  7. PMID 28431496
    .
  8. Journal of Arachnology
    . 26 (3): 257–272.
  9. PMID 21863011
    .
  10. ^
    PMID 24726154
    .

External links
Retrieved from "https://en.wikipedia.org/w/index.php?title=Harvestman_phylogeny&oldid=1186799084"