Major Groups of the genus Sennertia, family Chaetodactylidae

Bee Mites : Acari : Acariformes : Sarcoptiformes : Chaetodactylidae : Sennertia

Major groups of the genus Sennertia Oudemans, 1905

Subgenus Afrosennertia Fain, 1981 (subgenus in Sennertia, type species Sennertia monicae Fain, 1971, by original designation) (=Asiosennertia Fain, 1981 Fain, 1982, monicae-group Fain, 1974)

Subgenus Amsennertia Fain, 1981 (subgenus in Sennertia, type species Sennertia frontalis Vitzthum, 1941 by original designation)
americana-group Klimov and OConnor, 2008 (Sennertia, subgenus Amsennertia, based on Sennertia americana Delfinado and Baker, 1976)
ignota-group Klimov and OConnor, 2008 (Sennertia, subgenus Amsennertia, based on Sennertia ignota Delfinado and Baker, 1976)
faini-group Klimov and OConnor, 2008 (Sennertia, subgenus Amsennertia, based on Sennertia faini Baker and Delfinado-Baker, 1983
loricata-group Klimov and OConnor, 2008 (Sennertia, subgenus Amsennertia, based on Sennertia loricata Klimov and OConnor, 2008)
frontalis-group, Klimov and OConnor, 2008 (Sennertia, subgenus Amsennertia, based on Sennertia frontalis Vitzthum, 1941)
Subgenus Sennertia Oudemans, 1905 (subgenus in Sennertia) (=Eosennertia Kurosa, 2003)
cerambycina-group (Sennertia, subgenus Sennertia, based on Sennertia cerambycina (Scopoli, 1763)) (=Eosennertia Kurosa, 2003)
japonica-group Fain, 1981 (Sennertia, subgenus Sennertia, based on Sennertia japonicus (Oudemans, 1901) (=Sennertia japonica (Oudemans, 1900)
Subgenus Spinosennertia Fain, 1981 (subgenus in Sennertia, type species Sennertia argentina Vitzthum, 1941, by original designation)

Unranked devincta-group Klimov and OConnor, 2007 (Sennertia, based on Sennertia devincta Klimov and OConnor, 2007)
horrida-group Fain, 1981 (Sennertia, unranked, based on Sennertia horrida (Vitzthum, 1912))
surinamensis-group, Klimov and OConnor, 2008 (Sennertia, unranked, based on Sennertia surinamensis Fain and Lukoschus, 1971)
zhelochovtsevi-group Klimov and OConnor, 2008 (Sennertia, unranked, based on Sennertia zhelochovtsevi Zachvatkin, 1941)
vaga Klimov and OConnor, 2008 (Sennertia, unranked, based on adults Sennertia vaga Klimov and OConnor, 2008).

Notes. Although the monophyly of Sennertia is well supported (Klimov & OConnor, 2008), the internal relationships among different lineages and, especially their early divergence, are not clear. Sennertia zhelochovtsevi represents a mixture of advanced (the shape of hysterosomal shield) and plesiomorphic characters (relative length of si and c₁), and the latter indicate its early divergence. Several characters (length of setae c₁ and the reduction of hysterosomal sclerotization) suggest its possible sister-group relationship with the New World clades associated with Xylocopa.
With the extremely conservative and variable morphology in several distant lineages, the question about the monophyly of some Ceratina and Xylocopa associated lineages remains unsolved. The high rate of convergent morphological changes probably occurred because of correlated increase of the lengths of setae situated off the hysterosomal shield following its reduction. A preliminary phylogenetic analysis of several putative groups is given by Klimov and OConnor (2008).
Different groups of Sennertia phoretic deutonymphs are diagnosed in the following key (excludes the vaga-group, which is based on adults only):

Key to subgenera and species-groups of Sennertia
(phoretic deutonymphs, unique character states underlined)

Setae c₁ long, nearly as long as se. Setae si nearly as long as se

... 2

Setae c₁ shorter than se, microsetae. Setae si variable

... 8

2(1)

Hysterosomal shield triangle. Opisthosomal gland openings outside shield. Tarsal setae w IV short. Posterior apodeme IV absent. Xylocopa (Proxylocopa). Mediterranean, Middle Asia ... zhelochovtsevi-group (new)

Hysterosomal shield not triangle. Position of opisthosomal gland openings, length of tarsal setae w IV, and presence/absence of posterior apodeme IV variable. New World. (Amsennertia s. l.)

... 3

3(2)

Tarsal ventral setae w IV long, distinctly longer than leg IV. Posterior apodeme IV present. Setae 1a, 3a, 4b conoidal; c3, 4a, and g inflated at bases. Setae wa I-II bifid ... devincta-group

Tarsal ventral setae w IV distinctly shorter than leg IV. Posterior apodeme IV absent. Setae 1a, 3a, 4b, c₃, 4a, g, and wa I-II simple. Associated with Xylocopa. (Amsennertia s. str.)

... 4

4(3)

Setae d₁, e₁, and h₁ nearly uniform in length, microsetae, d₁ and e₁ distinctly shorter than respective 1/2 of distance between them. (-) Setae c₁ situated on anterior margin of hysterosomal shield (frontalis-, loricata-groups) or anterior to it (americana-group). Opisthosomal gland openings on (frontalis-group) or outside hysterosomal shield (loricata-group, americana-group)

... 6

Setae d₁ and e₁ distinctly longer than h₁, at least one of them longer than 1/2 of distance between bases. Setae c₁ anterior to hysterosomal shield. Opisthosomal gland openings outside hysterosomal shield

... 5

5(4)

Setae mG II almost as long as leg II, distinctly longer than vF II. Tarsal setae ra I-II simple ... ignota-group

Setae mG II distinctly shorter than leg II and setae vF II. Tarsal setae ra I-II bifid ... faini-group

6(4)

Setae c₁ anterior to hysterosomal shield ... americana-group

Setae c₁ situated on anterior margin of hysterosomal shield

... 7

7(6)

Opisthosomal gland openings outside hysterosomal shield. Usual striate pattern of hysterosoma accompanied by sclerotization ... loricata-group

Opisthosomal gland openings on hysterosomal shield. Striate pattern of hysterosoma without sclerotization ... frontalis-group

8(1)

Caruncle I-III with 2 distinct transparent lobes. Setae si distinctly longer than se. Tarsal setae e and f I-II strongly asymmetrical, f about 2 times shorter and filiform, e longer and lanceolate. (-) Hysterosomal shield triangle in outline. Setae pR I-II, sR III, wF IV, gT I-II, hT I-II, kT III, ra I-II, and wa I-II spiniform. Associated with Xylocopa in the Neotropics ... Spinosennertia Fain

Caruncle I-III with 1, usually sclerotized lobe (distal lobe absent). Tarsal setae e and f I-II slightly asymmetrical, f maximum 1.5 shorter than e. Other characters variable

... 9

9(8)

Setae c₁ anterior to hysterosomal shield. Associated with Xylocopa. Afrotropical, Oriental, Eastern Palaearctic ... Afrosennertia Fain (=Asiosennertia Fain)

Setae c₁ situated on hysterosomal shield. Associated with Xylocopa and Ceratina. Old World (Sennertia)

... 10

10(9)

Setae si of medium length, not microsetae

... 11

Setae si microsetae

... 12

11(10)

Ventral tarsal seta w IV long, distinctly longer than tarsus IV. Setae si and se on same transverse level (si distinctly posterior in one undescribed species). Associated with Xylocopa. Oriental region and Madagascar ... horrida-group

Ventral tarsal seta w IV short, usually shorter than tarsus IV. Setae si posterior to se. Associated with Ceratina. Neotropics ... surinamensis-group

12(10)

Ventral tarsal seta w IV elongated. Afrotropic and Oriental, Eastern Palaearctic. Associated with Xylocopa (placement of the African clade here is questionable) ... japonica-group

Ventral tarsal seta wa IV not elongated. Associated with Xylocopa or Ceratina. Old World. (probably paraphyletic) ... cerambycina-group (including Eosennertia Kurosa)

References

Klimov, P. B. & B. M. OConnor. 2008. Morphology, evolution, and host associations of bee-associated mites of the family Chaetodactylidae (Acari: Astigmata), with a monographic revision of North American taxa. Miscellaneous Publications Museum of Zoology University of Michigan.199: 1-243.