SIGNIFICANCE OF COLOUR POLYMORPHISM IN MOUNTAIN POPULATIONS OF ABUNDANT LEAF BEETLES
(COLEOPTERA, CHRYSOMELIDAE)

Y. E. MIKHAILEV

Dept. of Botany & Forest Protection, Urals State Forestry-Engineering University,
Sibirsky trakt, 37, 620100, Yekaterinburg, Rusia

ABSTRACT.- Leaf beetles, especially common and abundant species, play significant role in the flow of biomass and energy in alpine ecosystems. They feed openly in the leafage of shrubs and herbs and their various metallic colourations or highly melanistic forms absorb solar radiation, promoting warming and decreasing penetration of UV. Therefore colour polymorphism is important for monitoring of status of exact populations. Polymorphism as ecologically selected variability serves for the most complete and effective use of environmental heterogeneity. That is why composition of morphs and its changes in space and time are especially sensitive. Eco-geographical regularities of colour polymorphism is shown for various mountain populations of Chrysomela lapponica, Gonioctena arctica and Oreina sulcata throughout their distribution area. These species together with related ones enable to make a sensitive network of biosensors for climate change monitoring in Holarctic region.

RÉSUMÉ.- Les Scarabées des feuilles deviennent spécialement communs, pré-
sentent de nombreuses espèces et sans doute peuvent jouer un rôle important sur le
cycle de biomasse et le flux d'énergie des écosystèmes alpiens. Ces insectes mangent
les feuilles des arbrisseaux ou des herbes et leurs colorations métalliques très variées
ou leurs formes fortement mélaniques absorbent les radiations solaires; c'est comme
cela qu'ils provoquent un réchauffement et arrivent à filtrer les rayons UV. En con-
séquence, le polymorphisme de couleurs se montre très important pour le monitoring
de plusieurs populations concernées. Si nous considérons ce polymorphisme comme
un type de variabilité selectionnée écologiquement, il peut bien contribuer à une uti-
lisation plus effective et complète de l'hétérogénéité environnementale. C'est pour-
quoi la composition des morphotypes et ses changements aussi bien dans l'espace que
dans le temps deviennent très sensibles. Chez les populations montagnardes de
Chrysomela lapponica, Gonioctena arcaica et Oreina sulcata et au long de leur
aire de répartition ont été observées certaines régularités ecogéographiques du poly-
morphisme couleur. Sans doute ces espèces et d'autres semblables pourraient aider à
établir un réseau de bioindicateurs permettant un monitoring du changement cli-
matique sur la région Holartique.

RESUMEN.- Los escarabajos de las hojas resultan especialmente comunes, pre-
sentan numerosas especies y sin duda juegan un papel destacado en el ciclo de bio-
masa o en el flujo de energía de los ecosistemas alpinos. Estos insectos se alimentan
del follaje de arbustos o hierbas y sus variadas coloraciones metálicas o sus formas
altamente melánicas absorben la radiación solar; por ese procedimiento provocan un
calentamiento y filtran los rayos ultravioleta. Así, el polimorfismo de colores resulta
importante para el seguimiento de unas poblaciones determinadas. Considerado
dicho polimorfismo como variabilidad seleccionada ecológicamente, puede contribuir
a una utilización más completa y efectiva de la heterogeneidad ambiental. Esa es la
razón por la cual una composición de morfotipos y sus cambios en el espacio y en el
tiempo resultan especialmente sensibles. Ciertas regularidades ecogeográficas del
polimorfismo de colores pueden apreciarse en varias poblaciones montanas de
Chrysomela lapponica, Gonioctena arcaica y Oreina sulcata a lo largo de su
área de distribución. Tales especies y otras relacionadas permitirían el establecimien-
to de una red de biosensores para el seguimiento del cambio climático en la región
Holártica.

Keywords: Mountain biodiversity, population ecology, colour polymorphism, leaf beetles.

1. Introduction

Leaf beetles are not so diverse as other groups of alpine insects, but among
them there are representatives specifically associated with dominating plants
in subalpine and alpine ecosystems. The species of *Chrysomela* and *Gonioctena*
intensely feeding on prostrate willows, birch or mountain alder may com-
pletely defoliate the patches. The damage to perennial herbs is well seen
wherever beetles of *Oreina* spp. are feeding on them and its extent became the
subject for careful evaluation (PYSEK & BEZDEK, 1996). Thus these common
and abundant species of leaf beetles play significant role in the flow of bio-
mass and energy in alpine ecosystems.

Alpine insects openly feeding in the leafage of shrubs have two ways of
adaptation: either using only the lower part of it close to the soil (temperature
and humidity is higher and wind is light) or using the upper part, where they
can use solar radiation for heating themselves (BOGACHEVA, 1990). It was
found that various metallic colours (bronze, blue, green, violet, ets.) or high-
ly melanistic forms are common in mountain populations of leaf-beetles.
These colours absorb solar radiation more efficiently and promote warming,
but simultaneously decrease penetration of ultraviolet (LOPATIN, 1996). And
this is one of the explanations why colour polymorphism may serve well for
monitoring of exact populations under climate change. Furthermore, alpine
species of leaf beetles have undergone major habitat shifts during the last
glaciation and currently live in geomorphologically and climatically very
diverse environments (KNOLL & ROWELL-RAHIER, 1998). Therefore now
they have clear potential to act as sensitive biosensors of climate change.

**2. Materials and methods**

In the course of our research of diversity and ecology of alpine leaf beetles
in the mountains of the Urals, Altai, Kuznetsky Alatau, West Sayan, Tuva and
Swiss Alps in 1993-2001 we studied species composition and took represen-
tative samples from the populations of most abundant species. Such samples
were taken on different altitudes if it were possible.

Studying of colour pattern polymorphism, distinguishing of separate
morphs and constructing of polymorphic spectrums we made according to
the principles of population phenetics (YABLOKOV, 1987; MIKHAILOV,
1999). The determination of colour morphs in *Oreina sulcata* Gebler we made
using similar experience in other leaf-beetles with metallic colouration
(SUZUKI & OZAKI, 1980).

Data processing was made by means of standard PC software Excel and
Statistica.

**3. Eco-geographical regularities of colour polymorphism in selected species**

Chrysomela lapponica L.

Boreal-montane species widely distributed in Palaearctic from Western
Europe to Kamchatka and Japan, northward to Novaya Zemlya islands and
in alpine zone in Fennoscandia, the Urals, South Siberia and Tien-Shan
(MATIS, 1986; LOPATIN, 1996).

We observed beetles and their larvae very numerous and intensely feed-
ing on prostrate willow *Salix* spp. in the Urals and Kuznetsky Alatau mts.,
rarely on prostrate birch *Betula nana* (South Altai). In French Alps (Col Agnel)
this species was recorded on mountain alder *Alnus viridis*, which was com-
pletely defoliated (LEPLAT, 1999). On willows they skeletonise the leaves (up
to 100% of the leaf surface) remaining only nerves. Heavily feeding this leaf
beetle may damage 100% of leaves on some plants. Such plants with dry leaves are well seen in mt. tundra areas and among stones. Leaf-beetles, their larvae and pupae are living openly having defensive allomones from predators, which on willows are host-derived (PASTEELS et al., 1988). Mass emergence of beetles from pupae takes place in the last decade of June - early July (after hibernation) and in first decade of August (new generation).

By means of colour pattern polymorphism we studied structure of several populations in alpine zone of Kuznetsky Alatau (KA), SE Tuva, South Altai (Tarbagatai range) and North Ural. We obtained data on characteristic composition of morphs in these populations (Figure 1) using spectrum of morphs of elytral colour pattern (Figure 2).

All investigated populations clearly divided in two groups (Figure 1). In Kuznetsky Alatau and South Altai typical form (20) is dominating, while in East Tuva and the Urals - other, more melanized morphs. Frequencies of light (1-6) and completely dark-metallic (50) morphs also varies greatly (Figure 1). These characters are convenient for long term monitoring and also comparisons with chosen lowland populations.

Ch. lapponica is trans-Eurasian species and is available for research in lowlands, e. g. the Netherlands (BEENEN, 1985) and mountain populations in

<figure><img src="image_1.png" /><figcaption>Figure 1. Frequencies of morphs in various populations of *Chrysomela lapponica* (Note: KA - Kuznetsky Alatau mts., SA - South Altai).</figcaption></figure>
<figure><img src="image_2.png" /><figcaption>Figure 2. Polymorphic spectrum of colour pattern of *Chrysomela lapponica*.</figcaption></figure>

many points as well. And more, several closely related species: *Chrysomela interrupta* Brown, *Ch. alnicola* Brown, *Ch. walshi* Brown, *Ch. knabi* Brown, *Ch. falsa* Brown, *Ch. aeneicollis* (Schaeffer) are distributed in North America from lowlands to mountains and their variability is within the same spectrum (BROWN, 1956). All this related group might be used for coordinated monitoring network in Polarctic region as a whole.

*Gonioctena arctica* (Mannh.) (=affinis (Gyll.))

As previous species inhabits northern forest zone of Eurasia but also North America and have isolated populations in the mountains of Siberia and the Urals distant southward. Its exact populations are highly polymorphic (Figure 3) and have specific composition of morphs in every investigated point. Usually typical form dominates, also in the lowlands of Finland (SIL-FVERBERG, 1994), but the relic population of the South Ural differs from many others like isolated populations of Sakhalin Island.
<figure><img src="image_3.png" /><figcaption>Figure 3. Polymorphic spectrum of colour pattern of *Gonioctena arctica* (=G. affinis) (from KRESLAVSKY, 1975 with corrections and additions).</figcaption></figure>

*Gonioctena arctica* is abundant in all studied populations and feeding open-
ly on *Salix* species in mountain forest-tundra and tundra.

Oreina sulcata Gebl.

This species is very common and abundant in the mountains of South
Siberia. It inhabits Altai, the Sayans, mts. of Tuva, Cisbaikalia and
Transbaicalia. Isolated lowland populations are known from the Yenisei val-
ley northward to Arctic Circle and recently found in Tyumen region in
Western Siberia far away from the main distribution area (MIKHAILOV,
2000). Oreina sulcata prefers tall herb montane or subalpine meadows with its
host plants Saussurea latifolia (Asteraceae) and Heracleum dissectum (Apiaceae)
(Altai, Kuznetsky Alatau mts., West Sayan). The most high mountain popu-
lations were found in mountain tundra of SE Tuva near snowbeds (host plant
there unknown).

There are two forms distinguished mainly by the elytral sculpture (smooth or sulcate). They were initially described by GEBLER (1823) as two different species. In Russian works they have been treated as two subspecies - *Oreina basilea basilea* Gebl. and *O. basilea sulcata* Gebl. But recently it was shown that according to the principle of the first revisor this species must be called *O. sulcata* Gebl. (*O. basilea* is a synonym) and subspecies division was rejected due to continuous variation of elytral sculpture (BONTEMS, 2001). But there is
still a problem how to treat smooth and sulcate forms, from which the former
is dominating in the western part of distribution area (throughout Altai and
Kuznetsky Alatau mts.) and the latter - in the eastern part (the Sayans, moun-
tains of Tuva and Cisbaicalia) according both to our observations and BON-
TEMS (2001).

This species has very wide range of colour morphs: purple red, reddish-
brown, goldish-red, bronze, goldish-green, green, emerald, bluish-green,
blue, bluish-violaceous, violaceous, blackish-violaceous, black and striped.
The populations in various parts of distribution area have specific difference
in composition of morphs.

Previously it was noticed, that generally in the western part of its distri-
bution area beetles of O. sulcata of red and brown colour are more rare than
in eastern part, in West Altai blue beetles are abundant on high altitudes. In
the eastern part in some regions red beetles are dominating (KRESLAVSKY,
1975). But in fact main difference in composition of morphs first of all is
between two forms, or more likely races. Dark-bronze, red-brown and
bronze-green and emerald morphs are peculiar to sulcata race (polymorphic
spectrum is wider), while purple red morph - to basilea race. Other morphs
are common (Figures 4 and 5).

<figure><img src="image_4.png" /><figcaption>Figure 4. Frequencies of colour morphs in various populations of Oreina sulcata (basilea race).
(Note: KA - Kuznetsky Alatau mts., WA - West Altai, NA - North Altai, SEA - South-East Altai; original data, except * - data from DOLGIN, 1978).</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>Figure 5. Frequencies of colour morphs in various populations of *Oreina sulcata* (*sulcata* race) (Note: WS - West Sayan, ES - East Sayan).</figcaption></figure>

Also from the lowlands and foothills to subalpine meadows and mountain tundra this species has trends in composition of morphs of body colouration along altitudinal transects. Generally at the foothills green (together with goldish-green) morphs are dominating, while the higher above sea level the lower is their percentage. This correlation firstly was reported by DOLGIN (1978) but only based on three sites on various altitudes in North and Central Altai (two of them near Teletskoye lake is shown on Figure 4). We can prove this conclusion based on more sites (Figure 4) (for green and goldish-green morphs together) for *basilea* race in general and for populations of *sulcata* race from the Sayans. In other high ranges of East Tuva green and goldish-green morphs still dominates on the highest altitudes (Figure 5). In both forms the majority of other morphs appear on higher altitudes, usually 2000 m. a. s. l. and more (Figures 4 and 5).

The center of species diversity of the genus *Oreina* is situated in the mountains of South and Middle Europe - 22 species in 7 subgenera (KIPPENBERG & DÖBERL, 1994). Two Siberian species - *O.* (s. str.) *sulcata* Gebl. and *O.* (*Chrysochloa*) *redikortzevi* Jacobson - are both relics and represent only two subgenera.

In Europe population polymorphism is well studied in two species: *Oreina (Chrysochloa) cacaliae* (Schrank) and *O. (Chrysochloa) speciosissima* (Scop.), both distributed from NE Spain throughout the Alps to Karpatians, occur symmetrically feeding on the same host plant patches. Within populations individuals of both species show only minor colour variations. One of the explanations is that the colours are warning signals to possible predators. So mimicry and adaptation of individuals to the local dominating colour form
strongly restrict polymorphic spectrum in exact localities (KNOLL & ROWELL-RAHIER, 1998).

But also in general European species, including *Oreina cacaliae* (Schrank) and *O. speciosissima* (Scop.) has narrower polymorphic spectrum (KRESLAVSKY, 1975) in comparison with *O. sulcata*. This might be explained under niche - width variation hypothesis after VAN VALEN (1965). In Europe multispecies associations (gUILDS) are common on subalpine plants which include from 2 to 5 species of *Oreina* in one site (DOBLER, 1993; pers. obs.). Also usually several species are distributed along altitudinal gradients, changing one another from piedmonts to alpine zone. On the contrary, *O. sulcata* alone inhabits large mountain territories of South Siberia (only in some places of the Sayans in sympatry with *O. redikortzevi*) also along the whole altitudinal gradients, therefore its econiche is much wider. This is one of the explanations why *O. sulcata* – one of two species known from the mountains of South Siberia – has so wide polymorphic spectrum.

But despite different width of polymorphic spectrums European species also demonstrate similar regularities. For example, the colour of *O. cacaliae* showed a strong correlation with altitude: at higher altitudes beetles were dark blue, while lower - mostly green. (KNOLL & ROWELL-RAHIER, 1998). And this shows parallel trends with *O. sulcata* in Siberia.

## 4. Conclusion

Recognizing plants as the prime indicator organisms for the biological monitoring of climate change in alpine habitats, we consider other groups of organisms responding more rapidly and more predictably. The herbivorous insects specifically associated with common and widely distributed boreal plants provide better opportunities to develop longer term sampling networks. They have clear potential to act as more sensitive biosensors of climate change than their host plants (HODKINSON & BIRD, 1998). Among them leaf beetles (Coleoptera, Chrysomelidae), which have high abundances and present one of dominating groups in subalpine and alpine belts.

The distribution of host-specific herbivorous insects along latitudinal and altitudinal gradients may provide useful analogs for predicted future changes (HODKINSON & BIRD, 1998). But in fact the expected results would be very poor if biodiversity in this case is investigated on the species level only. However, biodiversity manifest itself on the population level as well and the most common example here is polymorphism (VASILYEV, 1996; MIKHAILOV, 1999). Polymorphism is ecologically selected variability, which
main function is the most complete and effective assimilation of environmental heterogeneity (SERGIYEVSKY, 1987).

Whether species track environmental changes is best evidenced by population structure. Composition and frequencies of morphs proved to be stable and specific in exact populations over a long-term observation period in various insects (NOVOZHENOV, 1989). At the same time a set of sensitive methods makes it possible to watch population structure changes, which track changes in their habitats. Firstly it was shown in anthropogenic biocoenoses (YEMETS, 1997; MIKHAILOV, 1998), but man made clearings under succession may be a model to some extent of predicted changes above timberline.

Several species of leaf beetles listed above would be among the key objects due to their high abundances, comparatively convenient collecting and complex of research methods already elaborated for monitoring of their population dynamics.

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