The possible hybrid origin of the feather mite Avenzoaria canuti ...

THE POSSIBLE HYBRID THE FEATHER MITE AVENZOARIA CANUTI
BIOLOGICAL LETT. 2006, 43(2): 119–130
Available online at http://www.biollett.amu.edu.pl
The possible hybrid origin of the feather mite Avenzoaria canuti
(Astigmata: Analgoidea) from the Red Knot Calidris canutus
(Aves: Charadriiformes) – a morphological approach
AGNIESZKA BADEK and JACEK DABERT*
Department of Animal Morphology, Faculty of Biology, A. Mickiewicz University, Umultowska 89,
61-614 Poznañ, Poland, dabert@amu.edu.pl
(Received on: 4 January 2006, Accepted on 14 May 2006)
119
Abstract: Biometric analysis of 81 morphological characters of 3 Avenzoaria species (Astigmata:
Analgoidea) was carried out to determine whether these characters distinguish naturally emerging groups
from analysed mite individuals. Discriminant analysis, based on the combination of variables that best
define particular species, showed significant morphological differences between mite populations
inhabiting various host species (especially for A. totani). Reconstruction of the ‘genetic structure’ (based
on phenotypic distances) of analysed populations (neighbour-joining procedure based on Mahalanobis
distances) revealed unusual relationships: females of A. canuti cluster with populations of A. calidridis,
while males are members of the A. totani clade. This suggests a possible hybrid origin of A. canuti from
A. calidridis and A. totani.
Key words: hybridization, discriminant analysis, phylogeny, oligoxeny, feather mites, Avenzoaria, Tringa,
Calidris
INTRODUCTION
Feather mites are a very numerous mite group with about 2 000 named species
(PROCTOR 2003) and about 16 000 to be discovered (DABERT 2005), belonging to 2
superfamilies Analgoidea and Pterolichoidea (suborder Astigmata). They live exclusively
on birds, mainly in various parts of plumage, but sometimes also on or in the
skin (e.g. Epidermoptidae) (DABERT & MIRONOV 1999). Both evolutionary and biological
relationships between feather mites and their hosts are very close and in many
cases the occurrence of particular mite species is limited to a single bird species
(monoxeny). However, some feather mite species show wider host ranges (oligo- and
polyxeny).
In our earlier studies on morphological and genetic differentiation of oligoxenous
feather mite species (BADEK 2004, DABERT et al. 2005), we analysed morphological
variation of oligoxenous species of the genus Avenzoaria Oudemans, 1905
*Corresponding author

120 Agnieszka Badek and Jacek Dabert
Fig. 1. Analysed species of the genus Avenzoaria. A – A. totani, male, dorsal view; B – A. totani, female,
dorsal view; C – A. canuti, male; D – A. canuti, female; E – A. calidridis: male, dorsal view; F –
A. calidridis, female, dorsal view

THE POSSIBLE HYBRID THE FEATHER MITE AVENZOARIA CANUTI
121
(Avenzoariidae, Avenzoariinae). Mites of this genus occur on the vane surface of wing
contour feathers in waders of suborders Charadrii and Scolopaci (Charadriiformes).
We selected 2 species for the analysis: A. totani (Canestrini, 1878) (Fig. 1 A–B) and
A. calidridis (Oudemans, 1904) (Fig. 1 E–F), which are commensals of tattlers (Tringa
L., 1758) and sandpipers (Calidris Merrem, 1804), respectively. These 2 species are
very similar according to discrete morphological characters but relatively distant
genetically (DABERT et al. 2001). Analysis of the variability of both quantitative and
discrete morphological characters was conducted to determine whether populations
of A. calidridis and A. totani inhabiting various host species differ significantly each
other and, if so, what is the taxonomic status of the possible differences. We had
previously found that the Avenzoaria population occurring on the Red Knot Calidris
canutus (L., 1766) that was formerly recognized as A. calidridis shows, apart from
their own characteristic features also typical characters of both A. calidridis and A.
totani. We gave this population a species rank and described it as a new species: A.
canuti (Fig. 1 C–D) (BADEK & DABERT 2005). In the present paper we show the
results of the morphological analysis of this species compared with ones made for
particular populations of A. calidridis and A. totani sampled from various host species.
Our main aim here was to reconstruct the phylogenetic relationships among these
mite populations and to hypothesize the origin of A. canuti.
MATERIALS AND METHODS
The material used in the present study originates from the acarological collection
of the Department of Animal Morphology, Adam Mickiewicz University, Poznañ,
and was sampled in Poland and South Africa in 1983-1991 (Table 1). Avenzoaria
Table 1. Basic information on the analysed mite samples
No. Avenzoaria Host species Location Date No. of specimens
species
measured
males females
1 A. totani Tringa glareola Turawskie Lake, Poland Aug 1984 17 23
2 A. totani T. glareola S³oñsk near Kostrzyn, Poland Jul 1987 22 20
3 A. totani T. glareola S³oñsk near Kostrzyn, Poland Jul 1988 12 17
4 A. totani T. stagnatilis S³oñsk near Kostrzyn, Poland Jul 1987 6 8
5 A. totani T. totanus Zagórów, Poland
May 1988 11 18
S³oñsk near Kostrzyn, Poland Aug 1988
6 A. canuti Calidris canutus Vistula Mouth, Poland
Aug 1985 14 65
Velddrif, South Africa
Nov 1991
7 A. calidridis C. alpina Vistula Mouth, Poland
Aug 1985 2 13
Sowiniec near Poznañ, Poland Sep 1990
8 A. calidridis C. minuta Sowiniec near Poznañ, Poland Sep 1985 3 39
Vistula Mouth, Poland
Sep 1990
S³oñsk near Kostrzyn, Poland Jul 1987
Velddrif, South Africa
Nov 1991
9 A. calidridis C. temminckii S³oñsk near Kostrzyn, Poland Jul 1987 14 28
10 A. calidridis C. ferruginea S³oñsk near Kostrzyn, Poland Aug 1988 8 40
Vistula Mouth, Poland
Aug 1990
11 A. calidridis C. alba Vistula Mouth, Poland
Aug 1990 15 19
Górki Wschodnie near Gdañsk,
Poland
Oct 1990

122 Agnieszka Badek and Jacek Dabert
Fig. 2. Ornamentation patterns of hysteronotal shield in particular Avenzoaria taxa. 1 = A. totani from
Tringa glareola population 1; 2 = A. totani from T. glareola population 2; 3 = A. totani from T. glareola
population 3; 4 = A. totani from T. stagnatilis; 5 = A. totani from T. totanus; 6 = A. canuti from Calidris
canutus; 7 = A. calidridis from C. alpina; 8 = A. calidridis from C. minuta; 9 = A. calidridis from C.
temminckii; 10 = A. calidridis from C. ferruginea; 11 = A. calidridis from C. alba. Numbers of T. glareola
populations refer to locations given in Table 1.
mites were mounted on slides in Faure medium (EVANS 1992) and examined using
a light microscope Olympus BH-2 with Nomarsky phase contrast. We measured 154
individuals of A. totani, collected from 3 Tringa species: T. totanus (L., 1758),
T. glareola L., 1758, and T. stagnatilis (Bechstein, 1803); 181 of A. calidridis from
5 Calidris species: C. alba (Pallas, 1764), C. ferruginea (Pontoppidan, 1763), C. minuta
(Leisler, 1812), C. alpina (L., 1758), and C. temminckii (Leisler, 1812); and 79 of
A. canuti from C. canutus. Biometric analyses of variation of 77 morphological quantitative
characters and 4 discrete ones (see: Appendix) were conducted for adult stages
of above-mentioned mites. The setal nomenclature follows GAUD & ATYEO (1996).

THE POSSIBLE HYBRID THE FEATHER MITE AVENZOARIA CANUTI
123
Fig. 3. Location of genital acetabula in males. A = aedeagus base located posteriorly to both pairs of
genital acetabula; B = aedeagus base located at the level of posterior pair of genital acetabula; C = aedeagus
base located between anterior and posterior pair of genital acetabula. Numbers refer to populations
mentioned in Fig. 2.
Fig. 4. Shape of the interior tooth of the postlobar membrane. A = rectangular with a concave terminal
margin; B = semicircular. Numbers refer to populations mentioned in Fig. 2.
Discriminant function analysis was used to detect if particular quantitative characters
make it possible to distinguish groups among the analysed Avenzoaria individuals,
and then the canonical variables were computed. The main aim of the study
was to discover, basing on quantitative morphological characters, the possible structure
of genetic distances of analysed populations. There are several evidences that
there is significant correlation between phylogenetic and morphological distances (e.g.
MARROIG & CHEVERUD 2001, DIAS et al. 2004). The phylogenetic tree was recon-

124 Agnieszka Badek and Jacek Dabert
Fig. 5. Results of the discriminant analysis for the populations of females (A, B) and males (C, D). A
and C = A. totani from various hosts (1–5) and A. canuti from C. canutus (6); B and D = A. canuti from
C. canutus (6) and A. calidridis from various hosts (7–11). Numbers refer to populations mentioned in
Fig. 2. Z1 and Z2 = values of 1st and 2nd canonical discriminant functions.
structed using the neighbour-joining (NJ) procedure as implemented in PAUP 4*
software (SWOFFORD 2002). We used a Mahalanobis distance (D 2 ) matrix as the source
data for reconstructing the phenogram. These are distances between 2 points (centroids)
in the multidimensional space defined by several correlated independent variables
and are commonly used to reveal a genetic structure from morphometric data
(e.g. MARROIG & CHEVERUD 2001, ACKERMANN & CHEVERUD 2002, HARVATI et
al. 2004, DIAS et al. 2004).
All the statistical analyses were carried out by means of Statistica 6.0 software.
The graphic visualization of the phylogenetic trees was made by TreeView 1.6.6
software (PAGE 2001).

THE POSSIBLE HYBRID THE FEATHER MITE AVENZOARIA CANUTI
RESULTS
125
Fig. 6. Summarized results of discriminant analysis for the populations of Avenzoaria totani, A. canuti
and A. calidridis. A = females; B = males. Z1 and Z2 = values of 1st and 2nd canonical discriminant
functions.
Discriminant function analysis
From 4 discrete characters, all turned out to be informative and useful for recognizing
differences between Avenzoaria populations from various hosts. Examples
of the results are shown in Figures 2–4.
The discriminant function analysis was carried out on 77 quantitative characters
separately for males and females (47 and 34 characters, respectively). It enabled
selection of 17 male characters and 9 female ones that differentiated the best between
all the populations of particular host species (P < 0.05). Scatter plots (Figs. 5, 6) and
the Appendix summarize the results.
On the basis of either males or females, populations of A. totani are not homogeneous
(Fig. 5A, C). Populations from Tringa glareola (1–3) cluster together and
are separated from remaining A. totani populations living on T. stagnatilis (4) and T.
totanus (5). In populations of females of A. calidridis, we can observe a tendency to
clinal variability along the gradient temminckii (9) – [alpina (7), ferruginea (10),
minuta (8)] – alba (11), with the 2 extremes of this cline, temminckii (9) and alba
(11), differing significantly (Fig. 5B). Particular populations of males of A. calidridis
cluster separately and somewhat differently from females but because of the
small number of individuals studied (especially from Calidris minuta and C. alpina),
the results are less credible than in the case of females (Fig. 5D).
In all cases the discriminant function analysis separated well the individuals of
A. canuti (from Calidris canutus) not only from A. totani but also from A. calidridis,
with which it has been considered conspecific for a long time. However, A. canuti
can be similar to A. totani in some characters (e.g. in distance between setae h1-ps1
or between d2-d2, location of genital acetabula, Fig. 3) and in others to A. calidridis
(e.g. in distance between setae e2-h1 or between d2-d2, ornamentation of hysterono-

126 Agnieszka Badek and Jacek Dabert
Fig. 7. Unrooted neighbour-joining trees for males and females. Host names are shown in parentheses.
Numbers in T. glareola designate the population locations given in Table 1.
tal shield, Fig. 2). It shows also intermediate proportions of 2 character states between
A. totani and A. calidridis (e.g. shape of interior tooth of the postlobar membrane,
Fig. 4).
A summary of results of the discriminant analysis for all 11 populations studied
is presented in Figure 6. It shows very clearly that for both males and females
we have to do with 3 morphologically distinct clusters of individuals that most probably
have a species rank.
Phylogenetic analysis
The results of the phylogenetic analysis are very surprising. The reconstructed
tree of males differs from female one for some clusters (Fig. 7).
In both trees, A. totani and A. calidridis populations are located in separate
clades, which supports their placement in different taxa (species?). There is a distinct
tendency in the cluster totani to differentiation of 2 monophyletic groups: (1)
originating from Tringa glareola; and (2) from T. totanus and T. stagnatilis. The
interpretation of the calidridis cluster is more uncertain because the pattern is based
on a very small number of males for Calidris alpina and C. minuta. Yet the reciprocal
relationships of the remaining taxa – C. alba, C. ferruginea, and C. temminckii
– is the same in both male and female trees.

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However, the most important result of the analysis is the different clustering
of A. canuti depending on the sex examined. This species joins the cluster of A. totani
populations in the cladogram reconstructed for males. In the female tree it falls among
the A. calidridis populations. It is worthy of mention that in both cases A. canuti does
not build a sister clade for respective species but is deeply nested in each of the
clusters.
DISCUSSION
The present analyses have confirmed our previous presumptions (DABERT 1991,
BADEK & DABERT 2005) that A. canuti from the Red Knot resembles in some respects
the species A. calidridis (e.g. rounded lacunae on the hysteronotal shield), and
in other respects A. totani (e.g. anterior location of genital acetabula, setae h1 not
reaching the margins of interlobar membranes). Moreover, A. canuti has also its own
characteristic features: females are bigger and have posterior legs extending much
more posteriorly than populations of the other 2 species.
It is difficult to state on the basis of our present knowledge exactly how A.
canuti originated. We consider the most likely hypothesis to be that A. canuti is a
hybrid between A. totani and A. calidridis. The main premise for such a statement is
provided by the unusual results of the phylogenetic analysis, where 2 different trees
for males and females were obtained. In the male tree A. canuti is in the middle of
the A. totani cluster, while in the female tree A. canuti is a member of the A. calidridis
clade. We hypothesize that A. canuti represents a hybrid of closely related species,
which by inhabiting a new host species achieved reproductive isolation from
both parental species. The behaviour of the host Calidris canutus may have preadapted
it to the role of a living ‘hybridization zone’. This sandpiper groups during
feeding into mixed flocks with other waders: calidrine sandpipers of the genus Calidris
(hosting A. calidridis), the Ruff Philomachus pugnax (with A. philomachi), and
tringine tattlers of the genus Tringa (with A. totani 1 ). By contrast, in breeding biotopes,
the Red Knot coexists with the Ruddy Turnstone Arenaria interpres (with
A. arenarii) (DABERT 1991). To test the hybridization hypothesis on the origin of
A. canuti, molecular sequencing data are necessary; this analysis is currently being
carried out in our lab.
The morphometric, discriminant, and phylogenetic analyses have revealed also
some consistent differences between A. totani populations inhabiting Tringa glareola
(Figs. 3, 5A, C) and other populations inhabiting both remaining host species. As
in the case of A. canuti, only DNA sequencing could help to verify the relationships
between these populations.
1 Other species of tringine tattlers host the feather mite species Avenzoaria tringae, A. australis, and
A. gambettae. However these particular waders do not coexist with Calidris canutus.

128 Agnieszka Badek and Jacek Dabert
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Associate editor: ANNA SKORACKA

THE POSSIBLE HYBRID THE FEATHER MITE AVENZOARIA CANUTI
APPENDIX
No. Characters Male Female
1–2 Idiosoma length (+)
P=0.0013
(+)
3–4 Idiosoma width (+) (+)
5–6 Length of pronotal shield (+)
P=0.0206
(+)
7–8 Width of pronotal shield (+) (+)
P=0.0099
9–10 Length of hysteronotal shield (+) (+)
11–12 Distance between setae se–se (+) (+)
P=0.0003
13–14 Distance between setae si–si (+)
P=0.0226
(+)
15–16 Distance between setae c2–c2 (+)
P=0.0400
(+)
17–18 Distance between setae c1–c1 (+) (+)
19–20 Distance between setae d1–d1 (+)
P=0.0006
(+)
21–22 Distance between setae d2–d2 (+) (+)
P=0.0000 P=0.0389
23–24 Distance between setae e1–e1 (+) (+)
25–26 Distance between setae e2–e2 (+)
P=0.0003
(+)
27–28 Distance between setae h1–h1 (+) (+)
29 Distance between setae f2–f2 (+)
P=0.0145
(–)
30–31 Distance between setae ps1–ps1 (+) (+)
P=0.0041 P=0.0146
32–33 Distance between setae c1–d1 (+) (+)
34–35 Distance between setae d1–d2 (+)
P=0.0126
(+)
36–37 Distance between opisthonotal gland openings gl–gl (+) (+)
P=0.0382 P=0.0088
38–39 Distance between setae d2 and opisthonotal gland opening gl (+) (+)
P=0.0435
40–41 Distance between opisthonotal gland opening gl and setae e2 (+) (+)
P=0.0055
42–43 Distance between setae e2–h1 (+) (+)
44–45 Distance between setae h1–ps1 (+) (+)
46–47 Distance between setae c3–c3 (+)
P=0.0305
(+)
48–49 Distance between setae 3b–3b (+)
P=0.0421
(+)
50–51 Distance between setae 3a–3b (+)
P=0.0021
(+)
52–53 Distance between setae 3b–g (+) (+)
54–55 Distance between setae g–4a (+)
P=0.0001
(+)
129
Characters used in the biometric analysis. Characters significantly discriminating between populations
from various hosts are shown with probability values. (+) = character analysed,
(–) = character absent and/or not analysed

130 Agnieszka Badek and Jacek Dabert
56–57 Distance between setae 4a–ps3 (+) (+)
P=0.0012
58 Distance between setae 3a–3a (+) (–)
59 Distance between setae g–g (+) (–)
60–61 Distance between setae 3a–g (+) (+)
62 Distance between setae 4a–4a (+) (–)
63 Distance between setae ps3–ps3 (+)
P=0.0181
(–)
64 Length of opisthosomal lobes (+) (–)
65 Length of setae f2 (+) (–)
66 Length of setae ps1 (+) (–)
67 Width of opisthosomal lobes (+) (–)
68 Distance between setae f2–h1 (+)
P=0.0474
(–)
69 Minimum distance between interlobar membranes (+) (–)
70 Maximum distance between interlobar membranes (+) (–)
71 Length of setae h1 (+) (–)
72 Location of genital acetabula (+) (–)
73 Shape of interlobar membranes (+) (–)
74 Number of knobs on adanal disc corolla (+) (–)
75 Ornamentation of hysteronotal shield (+) (–)
76 Shape of the interior tooth of postlobar membranes (+) (–)
77 Distance between setae h2–h2 (–) (+)
P=0.0308
78 Distance between setae ps3–ps2 (–) (+)
79 Distance between setae ps2–ps2 (–) (+)
80 Epigynium width (–) (+)
81 Epigynium length (–) (+)