Haliplus leechi Wallis and H. salmo Wallis: a new synonymy and sexual dimorphism in the relative eye separation (Coleoptera: Haliplidae)

2009·1.6 MB·English

by  Rex D Kenner

J. Entomol. Soc. Brit. Columbia 106, December 2009 25
Haliplus leechi Wallis and H, salmo Wallis:
a new synonymy and sexual dimorphism
in the relative eye separation (Coleoptera: Haliplidae)
REX KENNER^
D.
ABSTRACT
Examination of the holotypes, specimens in the type series and material from across
their geographical ranges for Haliplus leechi Wallis and H. salmo Wallis shows that the
two names are conspecific; H. salmo is placed as a junior subjective synonym of H.
leechi. A sexual dimorphism in the relative eye separation is present in members ofthis
complex, H. canadensis Wallis and H. subguttatus Roberts. Preliminary data suggest
that this dimorphism may also be present in other haliplid species. This dimorphism
should be taken into account in constructing keys for the determination ofhaliplids.
INTRODUCTION
Haliplus leechi Wallis and H. salmo Relative eye separation, the dorsal dis-
Wallis are very similar structurally. tance between the eyes divided by the head-
Haliplus leechi is a widespread (Vondel width, is a character frequently used in keys
2005) species described from material col- for the determination of haliplids (Wallis
lected in Stanley Park, Vancouver, BC. 1933; Holmen 1987; Vondel 1991, 1993,
Haliplus salmo was described from speci- 1995; Vondel and Spangler 2008). In his
mens recovered from the stomach ofa trout revision ofthe Nearctic species ofHaliplus
AB
caught in Jasper, and has a more re- Latreille, Wallis (1933) used this character
stricted distribution (Vondel 2005). Wallis in separating three species pairs: H. leechi
(1933), in his description of these species, and H. salmo, H. subguttatus Roberts and
admitted that “it is possible that one is but a H. salinarius Wallis, and H. immaculicollis
geographical race of the other”. However, Harris and H. robertsi Zimmermann. Leech
he felt that these two taxa could be sepa- (1964) showed that relative eye separation
rated based on differences in background was not a useful character in separating the
color, maculation, punctulation and relative second pair and noted an apparent sexual
eye separation. The results of an investiga- dimorphism in this character. Subsequently
tion of the taxonomic status of H. leechi both the second and third pairs were syn-
and H. salmo are reported here. onymized (Vondel 1991, 2005).
MATERIALS AND METHODS
The minimum distance between the separation, Rjo was calculated by dividing
eyes, 10, and the maximum headwidth, 10 by HW.
HW, were measured using an oeular mi- The holotypes and allotypes ofH. leechi
crometer on a stereomicroscope (Wild M5, and H. salmo and the paratypes of these
Leica MZ12.5). Specimens were positioned species in the Canadian National Collection
such that the structure being measured was of Insects (Ottawa, ON) were examined.
parallel to the optical plane. Relative eye The relative eye separation, Rio, was meas-
‘ Beaty Biodiversity Museum, University of British Columbia, 2212 Main Mall, Vancouver, BC, V6T
1Z4, CANADA, email: [email protected]
26 J. Entomol. Soc. Brit. Columbia 106, December 2009
ured for both these specimens and a number (San Francisco, CA), D. Kavanagh; Cana-
of other specimens previously identified as dian National Collection ofInsects (Ottawa,
H. leechi or H. salmo. Approximately a ON), Y. Bousquet; J.B. Wallis Museum
third ofthe males in these latter series were (University of Manitoba, Winnipeg, MB),
dissected to allow examination of the geni- R.E. Roughley; James Entomological Col-
talia. The dissected genitalia were exam- lection (Washington State University, Pull-
ined while they were floating in liquid, to man, WA), R. Zack; Michigan State Collec-
prevent possible distortion due to drying tion of Insects (Michigan State University,
and mounting. In addition, R|o was meas- East Lansing, MI), G. Parsons; Museum of
ured for specimens identified as H. subgut- Zoology, Invertebrate Section (University
tatus and H. canadensis Wallis. The speci- of Calgary, Calgary, AB), J.E. Swann;
mens examined are in the author’s codec- Spencer Entomological Museum
tion or were borrowed from the following (University of British Columbia, Vancou-
museums: California Academy of Sciences ver, BC), K. Needham.
RESULTS AND DISCUSSION
Specific status of H. leechi and H. effect. It appe.irs that there is a continuum
salmo. Wallis (1933) suggested that H. in elytral maculation, with H. salmo being
leechi and H. salmo could be separated by: at one extreme and the putative subspecies
i) background color, ii) maculation, iii) H. leechi carteri Leech (1949) at the other.
punctulation and iv) relative eye separation. Note that the latter has since been syn-
i) The color of preserved specimens is onymized with the nominate subspecies
often more a function of their previous (Vondel 2005). The maculation of the head
treatment than of the particular species in- and thorax are similarly variable and do not
volved (e.g. Kenner 2005). Wallis acknowl- provide a reliable character for separating
edged this when he suggested that the color H. leechi and H. salmo.
of the H. salmo type series may have iii) Examination of a large number of
“undergone some change” due to being specimens in the current complex suggests
recovered from the stomach of a trout. It is that the small differences in punctulation
the current author’s experience, based on seen between the two holotypes is within
the examination of large numbers of speci- the variation seen in the population as a
mens belonging to the H. leechi-H. salmo whole and does not seem sufficient to jus-
complex, that the apparent background tify erecting separate species.
color is variable but the variation is not iv) Wallis gives Rio ofthe H. leechi and
correlated with any other morphological H. salmo holotypes as 0.46 and 0.54, re-
character. spectively. The current author’s remeasure-
ii) One of the most obvious differences ment of the holotypes gives a smaller dif-
in the two holotypes is in the elytral macu- ference in Rio: 0.48 and 0.51, respectively.
lation, with H. leechi having elytral The mean RioS for the two type series {H.
blotches and H. salmo being immaculate. leechi. holotype, allotype and nine para-
However, the maculation in H. leechi is types; H. salmo'. holotype, allotype and five
variable, with some ofthe paratypes “losing paratypes) are 0.48 (range 0.46-0.50) and
almost all traces of spots on the 0.51 (range 0.50-0.52), respectively. Wallis
elytra” (Wallis 1933). On most H. leechi uses Rio < 0.50 {H. leechi) and Rio > 0.50
specimens with very reduced maculation, {H. salmo) in his key; this character does
one can still detect the position of at least not even correctly separate all members of
some of the elytral blotches, due to infus- the two type series.
cate ‘halos’ around the strial punctures in Rio was measured for 142 specimens
the appropriate positions. At least one of previously identified as either H. leechi or
the H. salmo paratypes shows this same H. salmo', these specimens are from a vari-
J. Entomol. Soc. Brit. Columbia 106, December 2009 27
Relative Eye Separation
Figure 1. The frequency distribution ofthe Relative Eye Separation, Rio, for specimens identi-
=
fied as Haliplus leechi and H. salmo including the type series for each. Wallis used Rio <0.50
H. leechi and Rio >0.50 = H. salmo to separate the two species. Rio for the holotypes of H.
leechi and H. salmo are 0.48 and 0.51 respectively.
A
ety of localities. histogram of Rio from nature ofall other characters given by Wal-
these specimens plus the specimens from lis to separate these two taxa, H. salmo is
the type series (Fig. 1), gives a unimodal placed as ajunior subjective synonym ofH.
distribution with a mean of 0.49 (range leechi. Haliplus leechi was chosen as the
0.44-0.54). It appears that there is a contin- senior synonym to maintain stability in the
uum in the values of Rio, which suggests literature as it is the much more widely rec-
that it is not a good character for separating ognized and cited name and to maintain the
these two species. tribute to Hugh Leech intended by Wallis
This leaves possible differences in the (1933).
male genitalia to separate these two species. Sexual dimorphism in the relative eye
The apparent differences in Wallis’s draw- separation. In the data from the Rjo inves-
ings of the aedeagi are largely an illusion tigation discussed above, the smallest val-
caused by the fact that Wallis did not draw ues of Rio are from male specimens while
the basal part ofthe aedeagus for H. salmo. the largest values are from female speci-
If his two drawings are overlaid, one finds mens, although there is extensive overlap.
that the differences are on the order of a This suggests that Riomay be sexually di-
linewidth. Examination of the mounted morphic. However, since headwidth is pro-
genitalia of the two holotypes shows that portional to size and is smallest in males
the only significant difference is in the and largest in females, this could actually
length of the digitus on the left paramere: be a dependence on size rather than on sex.
longer in H. salmo. Due to possible distor- To test for a possible sexual dimorphism
tions caused by drying and mounting, it is in the relative eye separation, the specimens
HW
not clear ifthis difference is real. Examina- were sorted by and the mean value of
tion of a large number of genitalia from Rio for each size group was calculated
A
both putative H. leechi and H. salmo speci- separately for males and females. paired
mens suggests that the difference is not r-test (Whitlock and Schluter 2009) with a
constant. null hypothesis of no difference in Rio for
Based on the similarity in the genitalia males and females gives a mean Rio(c5'-$)
ofthe two holotypes and the apparent clinal = -0.013 {t = -3.71, df= 15, P = 0.002). The
28 J. Entomol. Soc. Brit. Columbia 106, December 2009
null hypothesis can be rejected with a high gree of confidence and a sexual dimor-
degree of confidence. Since males and fe- phism in Rio is supported. Preliminary tests
males ofthe same size were compared, one on other species suggest that this dimor-
can conclude that there is a sexual dimor- phism may occur more widely in haliplids
phism in Rio for H. leechi, with females (Kenner unpublished). While the difference
averaging larger. in Rio for males and females of a given
To determine ifthis is also true in other species are not large, one can end up with a
species, similar tests were performed for H. situation, as the current author has, where
canadensis and H. subgnttatus. For H. males and females go to opposite sides ofa
canadensis: mean Rio((5'-?) = -0.016 (^ = - couplet using Rio as the primary character.
2.60, df= 8, P = 0.032); for H. subguttatus: Future keys should take this sexual dimor-
mean R,o(d'-?) = -0.016 (/ = -6.23, df= 10, phism into account when the difference in
P < 0.001). In both ofthese species the null Rio is not large for the taxa being separated.
hypothesis can be rejected with a high de-
ACKNOWLEDGEMENTS
I thank the CanaCol Foundation for a ley, Brad Hubley, Richard Zack and Dick
grant that made possible my visit to the Baumann for the gift ofspecimens and John
Canadian National Collection ofInsects and Swann for sending me specimens that fi-
Y. Bousquet for his generous hospitality nally pushed me into dealing with this is-
my
during visit; the listed Curators for the sue.
loan ofspecimens in their care; Rob Rough-
REFERENCES
Holmen, M. 1987. The aquatic Adephaga (Coleoptera) ofFennoscandia and Denmark. I. Gyrinidae, Halipli-
dae, Hygrobiidae and Noteridae. E.J. Brill/Scandinavian Science Press Ltd., Leiden, Netherlands, pp.
168.
Kenner, R.D. 2005. Redescription ofHaliplus dorsomaculatus (Coleoptera: Haliplidae) with a new synon-
ymy and comments on habitat and distribution. Journal ofthe Entomological Society ofBritish Columbia
102:43-56.
Leech, H.B. 1949. Some Nearctic species ofHydradephagid water beetles, new and old (Coleoptera). The
Canadian Entomologist 80: 89-96.
Leech, H.B. 1964. Haliplus subguttatus Roberts from Washington and Oregon (Coleoptera: Haliplidae).
The Wasmann Journal ofBiology 22: 323-329.
Vondel, B.J. van 1991. Revision of the Palaearctic species of Haliplus subgenus Liaphlus Guignot
(Coleoptera: Haliplidae). Tijdschrift voor Entomologie 134: 75-144.
Vondel, B.J. van 1993. Revision ofthe Liaphlus species ofthe Oriental region excluding China (Coleoptera:
Haliplidae). Tijdschrift voor Entomologie 136: 289-316.
Vondel, B.J. van 1995. Haliplidae: Review ofthe Haliplidae ofChina (Coleoptera). Pp. 111-154. In M.A.
Jach and L. Ji (eds.): Water Beetles of China. Vol. I. Wein: Zoologisch-Botanische Gesellschaft in
Osterreich and Wiener Coleopterologenverein, 410 pp.
Vondel, B.J. van 2005. Family Haliplidae (Coleoptera: Adephaga). Pp. 20-86, in Nilsson, A.N. and Vondel,
B.J. van. 2005 Amphizoidae, Aspedytidae, Haliplidae, Noteridae and Paelobiidae (Coleoptera,
Adephaga). In: World Catalogue ofInsects 7: 1-171.
Vondel, B.J. van and P.J. Spangler. 2008. Revision of the Haliplidae of the Neotropieal Region including
Mexico (Coleoptera: Haliplidae). Koleopterologische Rundshau 78: 69-194.
Wallis, J.B. 1933. Revision ofthe North American species, (north ofMexico), ofthe Genus Haliplus, La-
treille. Transactions ofthe Royal Canadian Institute 19: 1-76.
Whitlock, M.C. and D. Schluter. 2009. The Analysis ofBiological Data. Roberts and Co. Publishers, Green-
wood Village, CO. pp. xxxiii, 700.