Small-tailed Worm (Allolobophoridella eiseni)

## Source: d-nb.info

Abstract

In a long-term survey of the Strict Forest Reserves in Hesse (Central Germany) a faunistic inventory was conducted using a

wide range of traps and hand sampling over a period of two years. Five of the six sites are beech forest types (dominating: Fagus

sylvatica), and one is a floodplain oak forest (dominating: Quercus robur). Although no special research program was run for

the earthworms, pitfall traps and eclectors at tree trunks and logs provided an unexpectedly high number (9 to 13) of species of

earthworms. A comparison of data from pitfall traps and trunk eclectors shows that highly different sets of lumbricids do occur in both

types. In the pitfall traps Lumbricus rubellus (22–43 % of adults) and Dendrobaena octaedra (10–16 % of adults) were dominant.

In the trunk eclectors the community consisted mainly (60–83 %) of Allolobophoridella eiseni. In addition, Dendrodrilus rubidus

(3–25 %) and Dendrobaena octaedra (6–16 %) were regularly found in these eclectors. Based on our findings Allolobophoridella

eiseni is a regular element of the invertebrate fauna of forests, occurring both in decaying logs and predominantly at the bark of

living and dead trees. Therefore, this species can be classified as predominantly corticolous. For the first time it could be proven that

Allolobophoridella eiseni regularly climbs on trees, which it does surprisingly mainly in late-autumn and in the winter.

89 (2) · August 20171. Introduction

In 1990 the Government of Hesse (Germany), in

cooperation with the Senckenberg Institute, started a

long-term survey of the fauna in Strict Forest Reserves

(= Naturwaldreservate) of Hesse; these are forest

areas that are allowed to mature without direct human

influence. In order to achieve a complete-as-possible

faunal inventory, many different sampling methods were

applied (Dorow et al. 1992), among them pitfall traps and

eclectors at standing and lying trees. Surprisingly, with

these two methods a high number of earthworm species

and individuals were collected, the dominant species

being Allolobophoridella eiseni (Levinsen, 1884).

Allolobophoridella eiseni is widespread in western

(including the United Kingdom), central and south-

eastern Europe, north-western Africa (Omodeo et al.

2003), several Atlantic islands, four states of the USA

(Arkansas, Oregon, Tennessee, Washington) (Reynolds

1995), New Zealand, Tasmania and South Africa (Sims

& Gerard 1999, Blakemore 2008). Csuzdi & Zicsi (2003)

classified it as a peregrine species with Atlantic origin.

Among the lumbricid earthworms of Central Europe,

Allolobophoridella eiseni (Levinsen, 1884) is peculiar

for various reasons. Firstly, its generic affiliation has

been highly controversial. Originally described as

Lumbricus eiseni (Levinsen 1884), it was later placed

at certain times in Allolobophora, Bimastus/Bimastos,

Dendrobaena, Eisenia and Helodrilus (in alphabetical

order, for details see Csuzdi & Zicsi 2003). Finally, Mršić

(1990) erected the new genus Allolobophoridella and

designated Lumbricus eiseni as its type species.

Secondly, and despite the fact that it has been found all

over Germany (Lehmitz et al. 2014), it is rarely found when

using the most common and already standardized methods

to sample earthworms, i.e. hand-sorting of soil samples or

extraction of earthworms from deeper soil layers by using

chemicals such as formalin (ISO 2006). Graff (1953) and

Bouché (1972) considered it a rare species in Germany

and France, respectively. The classification as ‘moderately

common’ and ‘not endangered’ in Germany (Lehmitz et al.

2016) is partly based on the data presented here.

And thirdly, the ecology of this species differs from

that of almost all other earthworm species in Europe,

since it does not prefer soil but aboveground habitats – a

preference well-known from some tropical earthworms

(e.g. Lee 1985, Fragoso & Rojas-Fragoso 1996), which

are regularly found on trees, often in bromeliad rosettes,

filled with canopy debris (Richardson et al. 2006), i.e.

mineral particles and decaying organic matter.

Traditionally earthworms are classified into three

ecological types (1) mineral dwellers (endogeics =

endogées), (2) litter dwellers (epigeics = épigées) and (3)

species living in vertical burrows (anecic = anéciques).

This concept was developed independently by Lee (1959)

and Bouché (1971), working on Pacific Islands and in

France, respectively. Furthermore, Lee (1959) realized

that a minority of earthworm species does not live in

soil but actually aboveground, on or in trees; for these

‘arboreal’ species he erected further groups: species (1)

living under the bark of standing trees or fallen logs,

(2) living in rotting logs and (3) living at the bases of

epiphytes and in leaf axils of understorey forest trees (for

a summary see Lee 1985). Bouché (1972) made similar

observations and defined – among others – one subgroup

of epigeic earthworms as ‘corticoles’, i.e. those living

below the bark of trees. In fact, he already mentioned

Allolobophoridella eiseni (sub Lumbricus) as a typical

example of this group. The concept of three ecological

groups of earthworms became widely accepted, and

further differences were conceptualized as subgroups,

especially when referring to the tropics (Lavelle 1984):

endogeics were subdivided based on feeding differences

and epigeics were subdivided based on their vertical

distribution. For those epigeic species living under

the bark of trees or on trees the terms corticolous and

arboreal are used (e.g. Lee 1985, Sims & Gerard 1999).

However, both terms are often used interchangeable.

Based on the data presented in the present contribution,

Lehmitz et al. (2014) classified Allolobophoridella eiseni

(Levinsen, 1884) as being corticolous, but with the note

‘often under bark of deadwood’. Only one further species

– out of 46 in Germany – was classified in a similar way;

this species, Eisenia lucens (Waga, 1857), seems to prefer

‘fallen logs under bark’.

Here we present a comparison of the numbers and

percentages of earthworms found in pitfall traps and

eclectors at standing and lying trees in six Strict Forest

Reserve sites of the federal state of Hesse. Even though

abundances cannot be calculated, these data clearly show

that A. eiseni is (1) a truly arboreal species and (2) more

common in Germany than previously assumed.

2. Materials and methods

The data presented here were gained in six Strict Forest

Reserves and their adjacent managed sites in Hesse,

central Germany (Fig. 1). Five of the six sites are beech

forests (dominating: Fagus sylvatica) in low mountain

ranges, and one (Kinzigaue) is a lowland floodplain oak

forest (dominating: Quercus robur) located in a flooding

area of a brook.

The fauna of the six Strict Forest Reserves and

five adjacent managed sites in Hesse, Germany, was

investigated over a period of two years (24 months) each,

using diverse techniques: pitfall traps; different types of

trunk eclectors on standing, lying, dead and living tree

trunks, stumps, dead branches; blue, white and yellow

pans; window traps. For details of the research concept

see Dorow et al. (1992). Table 1 shows the numbers of

trunk eclectors and pitfall traps in the reserves. Details on

the study areas – beech forests in colline areas (300-690 m

a.s.l.) except Kinzigaue, a lowland floodplain pedunculate

oak-hornbeam-forest (110 m a.s.l.) – can be found in the

following monographs: Goldbachs- und Ziebachsrück:

Dorow et al. (2009, 2010), Hohestein: Flechtner et al.

(2006), Dorow & Kopelke (2007), Kinzigaue: Blick et al.

(2012, 2014), Niddahänge östlich Rudingshain: Flechtner

et al. (1999, 2000), Schönbuche: Dorow et al. (2001, 2004),

with special contributions on the earthworms (Römbke

1999, 2001, 2006, 2009, Römbke et al. 2012) The data

on the earthworm fauna of the reserve Hasenblick and

its adjacent managed site are not published yet. A brief

overview of the reserves can be found online (IBV 2016).

The pitfall traps were constructed as follows: a 20 cm

long plastic tube sunk in the ground with a 10 cm wide

opening, leading via a plastic funnel into a collecting

glass; the trap was covered with a metal roof against rain

and leaf fall about 2 cm above the ground. The numbers of

pitfall traps varied according to the vegetation structures

present at each site.

There were different types of trunk eclectors:

Eclector at standing tree trunk: fyke-like trap-type that

collects animals walking up a tree trunk; this type was

used on living trees and on standing dead trees; the traps

were placed in a height of 1.8–2.0 m (Fig. 2A,B).

Eclector at lying tree trunk: a combination of two

different traps: (1) a 1 m long tube made of plastic and

metal, fixed at the two sides with cloth to the trunk to

collect animals that emerge from the trunk; (2) on both

sides a cloth-collar attached to collect animals walking on

the trunk surface. There are two sub-types: (1) trunks with

only little contact to the ground (Fig. 3) and (2) trunks

mostly lying on the ground (Fig. 4).

The ecletors could not be used on lying tree trunks in

several managed sites, because there were no such trunks

available. All eclectors had devices to collect species with

positive as well as negative phototaxis (= negative and

positive geotaxis, respectively).

Figure 2. Eclectors at standing trees.

Table 1. Research sites and number of trunk eclectors and pitfall traps. GZ = Goldbachs- und Ziebachsrück, HB = Hasenblick, HO =

Hohestein, KI = Kinzigaue, NI = Niddahänge, SB = Schönbuche; S = strict reserve area (no forestry management), M = area with forestry

management.

Table 1. Research sites and number of trunk eclectors and pitfall traps. GZ = Goldbachs- und Ziebachsrück, HB = Hasenblick, HO =

Hohestein, KI = Kinzigaue, NI = Niddahänge, SB = Schönbuche; S = strict reserve area (no forestry management), M = area with forestry

management.

GZ HB HO KI NI SB

Trap type S M S M S M S S M S M

Eclector at living tree trunk 2 2 2 2 2 2 2 2 2 2 2

Eclector at standing dead

tree trunk 2 2 2 2 2 2 2 2 2 2

Eclector at dead tree trunk

mostly lying on the ground 1 1 2 1 1 2 2 1

Eclector at dead tree trunk

with little contact to the

ground 1 1 1 1 2 1

Pitfall traps 27 29 54 33 24 21 36 27 25 18 19

All traps were run with a mixture of 70 % alcohol +

99.5 % glycerine in a 2:1 ratio as preserving fluid. For

details see Dorow et al. (1992).

All samples were emptied once per month, except in

winter where the traps where not emptied for four to five

months (exposition time: December to March/April).

3. Results

3.1 Dominant earthworms in the three

main trap types

Table 2 shows percentages of species finds in the

different collecting devices. All in all we collected 1418

adult Lumbricidae in the trunk eclectors at standing

trees, 294 in the trunk eclectors at lying trees and 865 in

the pitfall traps. Trunk eclectors and pitfall traps showed

different sets and percentages of lumbricids. In the trunk

eclectors at standing and lying trees the community

consisted predominantly (60–83 %) of Allolobophoridella

eiseni, with slightly higher percentages at standing trees

compared to lying logs. This species was trapped at

living beech trees (63 %) and at standing dead beech trees

(81 %). Also Dendrodrilus rubidus reached percentages

of 21–26 % at the trunks in the beech forests, but not at

the lying trunks in the floodplain oak forest. In contrast,

Dendrobaena octaedra was collected in all eclectors

and the pitfall traps with similar percentages (6–10 %),

except in the pitfall traps of the beech forests (16 %). In

the pitfall traps Lumbricus rubellus was by far the most

abundant species (43 % in the beech forests and 22 %

in the floodplain oak forest), followed by Dendrobaena

octaedra in the beech forests (16 %). In the oak forest

Allolobophoridella eiseni reached a percentage of 20 %

in the pitfall traps, followed by Lumbricus rubellus and

Aporrectodea limicola (the latter two being well known

for their preferences of moist to wet places).

Dendrodrilus rubidus (21 % in beech forests and 3 %

in the floodplain oak forest) as well as Dendrobaena

octaedra (7 % in beech forests and 9 % in the floodplain

oak forest) were also regularly found in trunk eclectors at

standing trees, meaning that they are also able to climb up

tree trunks (Tab. 2). The latter species was also abundant

in pitfall traps (10–16 % in both forest types), while the

former one prefers clearly the drier beech stands.

3.2 Phenology of Allolobophoridella eiseni

In the following the total and mean numbers of

Allolobophoridella eiseni in the three main trap types

per month and per half year are presented (Tab. 3). In

total, 1304 individuals of Allolobophoridella eiseni were

caught in the three types of traps. Most of them (1011)

were found in the traps on standing (living or dead) trees.

But there were fewer traps on lying than on standing

trees; due to the different trap types the absolute numbers

cannot be compared directly. Therefore in Fig. 5 the

relative numbers are used. In the traps on standing trees

only one third of all Allolobophoridella eiseni specimens

was found in the summer half year, while in the pitfall

traps their number was almost six times higher in the

summer than in the winter.

When looking at the numbers over the whole year the

highest numbers were almost always found in the traps

on standing trees, especially in the winter (Fig. 5). In

addition, there was only one month (August) in which

the numbers at the standing trees were lower than at the

lying trees, but in this month the total number was the

absolute minimum.

In general, only few Allolobophoridella eiseni were

caught in the pitfall traps (103, of these 63 in the reserve

Kinzigaue). Surprisingly, the highest number did occur

in July, a month of usually low earthworm activity

because of high temperatures and low soil moisture. In

contrast, in the winter half year the numbers in the pitfall

traps were small.

Table 2. Lumbricid species (in % of total number of adults) in the three main trap types (TS = trunk eclectors at standing trees, TL = trunk

eclectors at lying trees, PT = pitfall traps on the ground) and shown separately for beech forests (B) and the floodplain oak forest (O).

TS TL PT

B O B O B O

Allolobophoridella eiseni (Levinsen, 1884) 70.8 83.1 59.5 75.5 7.4 19.6

Aporrectodea caliginosa (Savigny, 1826) 0.1 7.0 5.9

Aporrectodea handlirschi (Rosa, 1897) 1.7 1.1 0.9

Aporrectodea limicola (Michaelsen, 1890) 0.4 16.5

Aporrectodea longa (Ude, 1885) 0.2

Aporrectodea rosea (Savigny, 1826) 0.1 0.5 1.1 0.6 1.9

Dendrobaena octaedra (Savigny, 1826) 6.5 8.5 8.0 8.5 16.2 9.9

Dendrodrilus rubidus (Savigny, 1826) 21.1 3.4 25.5 6.4 6.6 4.3

Eisenia fetida (Savigny, 1826) 0.1 2.0

Eiseniella tetraedra (Savigny, 1826) 0.2 2.5

Helodrilus oculatus Hoffmeister, 1845 0.7 0.2

Lumbricus castaneus (Savigny, 1826) 2.5 5.3 7.2 11.2

Lumbricus meliboeus Rosa, 1884 0.6

Lumbricus rubellus Hoffmeister, 1843 0.4 1.5 2.1 42.9 21.7

Lumbricus terrestris Linnaeus, 1758 0.5 2.6 3.4

Octolasion cyaneum (Savigny, 1826) 4.4 2.2

Octolasion tyrtaeum (Savigny, 1826) 3.7

Totals of adult Lumbricidae 1359 59 200 94 543 322

Table 3. Numbers of Allolobophoridella eiseni in the three main trap types (TS = trunk eclectors at standing trees, TL = trunk eclectors at

lying trees, PT = pitfall traps on the ground) per month, in total, and as percentages of the total sum per half year

Month/Totals Standing Lying Pitfall

V 91 19 13

VI 50 11 6

VII 53 28 34

VIII 7 16 12

IX 35 3 7

X 98 12 16

XI 248 59 9

XII-IV 429 42 6

Total 1011 190 103

V–X ‘summer’ (%) 33.0 46.8 85.4

XI–IV ‘winter’ (%) 67.0 53.2 14.6

Percentage of total sum 100.0 100.0 100.0

4. Discussion

Based on these findings it can be stated that

Allolobophoridella eiseni is a regular element of the

invertebrate fauna of forests, which can be trapped

predominantly at the bark on living trees, dead trees

(including decaying logs) and less frequently (with

exception of the moist oak forest) in pitfalls traps.

Therefore, this species can be classified as predominantly

arboricolous. For the first time it could be proven that

Allolobophoridella eiseni regularly climbs on trees

(Römbke et al. 2006) and is much more often caught

in this habitat than in the litter layer, i.e. it is truly an

arboreal species.

The occurrence, diversity and ecology of earthworms

living on or at trees are not well-studied. Records from

temperate regions are scarce, but Moeed & Meads (1983)

mention that about 1 % of all invertebrates caught in up-

and down-traps at trees in a New Zealand broadleaf/

podocarp and a nearby hard beech forest were earthworms.

No further details regarding the species are known, but

fewer worms were caught in summer compared to winter.

Actually, this behaviour is mainly described from tropical

regions where arboreal earthworm species are found

regularly (Lee 1985, James & Brown 2006, Richardson et

al. 2006). According to Fragoso & Rojas-Fragoso (1996),

there are two reasons why worms live on trees: either this

behaviour is a temporal shift in order to avoid seasonal

flooding of soils — e.g. in Amazonian lowland forests,

such as the glossocolecid Tuiba dianae Righi, Ayres

& Bittencourt 1976 (Adis & Bogen 1982: sub Tairona

tipema) or the rhinodrilid Andiorrhinus venezuelanus

tarumanis (Righi, Ayres & Bittencourt, 1976) (Adis &

Righi 1989) — or it is a permanent response to acidity and

low oxygen content of soils that occur in very wet tropical

forests (Lee 1983). In any case the aboveground habitat

has to be moist, meaning that such behaviour is often

found in mountainous or cloud forests (e.g. James 2010).

Further reasons are conceivable. For example Gaume

et al. (2006) reported on a megascolecid earthworm

species (Perionyx pullus Stephenson, 1920) that occurs

together with at least four different ant species on the

myrmecophytic understorey tree Humboldtia brunosis

(Fabaceae) in the Western Ghats, India, but the nature of

their interaction is not yet clear.

However, the factors given above do not fit well to

the ecological conditions in temperate regions such as

Central Europe: here, we assume that the availability

of food as well as the protection gained on trees or in

rotten wood is attractive for at least some litter-dwelling

species, especially Allolobophoridella eiseni. The lack of

competition with other lumbricids in this ‘new’ habitat

might be another factor. Unfortunately, information

on the climbing abilities of earthworms in general and

of Allolobophoridella eiseni in particular is scarce.

More or less anecdotal observations on earthworms

climbing vertical objects have been reported. Probably

the first example was given by Kuusinen (1962), who

observed individuals of the epigeics Eisenia fetida and

Dendrodrilus subrubicunda climbing up and down

on house walls, especially during night rains after dry

periods. The author explained this behaviour with

oxygen deficiencies in the soil. Similar observations were

regularly discussed on the internet, but always without

detailed information on the species.

Epigeic species (at least the adults) at German acid forest

sites have their activity minimum in the summer months

when the litter layer is usually very dry (see Römbke

1985), e.g. Dendrodrilus rubidus and Lumbricus rubellus.

In contrast, these worms are active in winter, provided

that litter layer and the uppermost mineral soil layer are

protected against freezing by a snow cover. This pattern

was found in this study as well, at least when looking at

the results of the traps on standing trees. The relatively

high number in the August pitfall traps is caused by high

numbers of individuals at the partly flooded site, which

was probably still moist. Of course, the worms living on

trees or deadwood cannot be protected by a snow cover,

but they may gain protection against freezing on the

tree by staying at specific sites where decaying organic

matter is accumulated (e.g. in tree holes, bark pockets,

phytotelmata, epiphyte-assemblages in natural habitats

or in roof gutters in the urban environment).

Regarding the habitat preferences of Allolobophoridella

eiseni, the literature accounts are varied. Zicsi (1965)

mentions it as a typical example for the corticoles, i.e.

species living below the bark of trees, for Austria. This is

supported by Bouché (1972) for France . Csuzdi & Zicsi

(2003) state, that all Hungarian individuals belonging to

this species live solely under the bark of decaying logs.

In contrast, Sims & Gerard (1999: 98) report that in

Great Britain Allolobophoridella eiseni is found ‘under

moss and decaying leaves, [being] often the dominant

earthworm in moorland, bog soils and by streams’.

Allolobophoridella eiseni seems to be temperature-

tolerant since it had been found not only in Central

Europe but also quite far north, especially in wet acid

moorlands of the Scottish islands. Similarly, Fender

(1985), who found Allolobophoridella eiseni in coastal

forests of the north-western United States (i.e. Oregon

and Washington), states that ‘these worms require cool,

even temperatures, high rainfall, an acid medium, and

high amounts of organic matter’. Omodeo et al. (2003)

found Allolobophoridella eiseni at seven Algerian and

two Moroccan sites (with one exception [grassland]

always in forests) and classified it as being typically

litter-dwelling but also as corticolous. In most of these

studies, no information is provided which methods were

used to collect Allolobophoridella eiseni.

Satchell (1955), referring to British forests, classified

Allolobophoridella eiseni as an acid-tolerant species, with

a preference of soil pH values of 3.7–4.7. Bouché (1972)

classifies Allolobophoridella eiseni as an acidophilous

species, i.e. preferring low soil pH-values. This statement

is supported by Sims & Gerard (1999) who report

occurrence in U.K. soils with a pH between 3.6 and

7.6. In contrast, most anecic and endogeic earthworm

species prefer pH-ranges >4.5 (Graefe & Beylich 2003),

meaning that Allolobophoridella eiseni is exceptional in

tolerating acidic as well as neutral conditions. Satchell

(1967) found correlations between the occurrence of

Allolobophoridella eiseni and the oxidation-reduction

potential, but mentions that such correlations are

interfered with by other factors such as soil moisture

or organic matter content. Höser (2013) considers

Allolobophoridella eiseni a peregrine species belonging

to the fauna of acid beech wood forests, referring to

findings of Römbke (1985, 2009). In summary, it seems

that Allolobophoridella eiseni is very tolerant in terms of

several ecological factors. It has been found in very cool

and wet (e.g. north-western USA) as well as in very warm

and dry places (e.g. northern Africa). In addition its pH

range of 3.6 to 7.6 is also relatively wide, like in most

epigeic, acidotolerant lumbricid species.

Allolobophoridella eiseni was found already in

the Hessian region Vogelsberg by Eggert (1982: sub

Bimastos eiseni). In total, 23.6 % of the earthworms

found by him under the bark of living trees belonged

to this species. In one case the species was caught at a

height of about 2 m under moist moss on an apple tree.

Römbke (1985: sub Bimastos eiseni) found just one

individual of Allolobophoridella eiseni (out of a total of

1143 lumbricids) in the mineral soil of a moder beech

forest in Baden-Württemberg (south-western Germany).

In contrast, six out of 15 earthworms caught in head-

boxes of ground-photo eclectors belonged to this species,

indicating its ability to climb on smooth surfaces, since

the collection box was located about 1 m above the litter

layer – and the way up was not vertical but overhanging.

Individuals of Allolobophoridella eiseni were found

even in branch traps in the crowns of oaks in a Bavarian

beech wood forest 15–22 m above ground (Goßner, pers.

comm.). Interestingly, this site is also located in a low

mountain range (520–535 m above sea level and with

an annual precipitation of 750–800 mm). These results

confirm that Allolobophoridella eiseni can be classified

as a predominantly corticolous or arboreal species.

The feeding behaviour of worms is clearly correlated

with their way of life (Lee 1985). Epigeics feed on

litter and/or the attached microflora with little or no

soil being ingested. Little specific information on the

feeding habits of Allolobophoridella eiseni is available.

Svendsen (1957) reports that in Scottish moors this

species is more often found under cattle dung pads than

in the remaining grassland, which may be caused by

their high amount of protozoans and nematodes (Holter

1983). In the laboratory, Allolobophoridella eiseni also

feeds on pine litter, accelerating the decomposition of the

Jörg Römbke et al.82SOIL ORGANISMS 89 (2) 2017

needles (Heungens 1969). The role of algae in the diet

of earthworms is still not clear (Edwards 2004). Surely

they will be digested when taken up together with soil,

but no specific grazing behaviour of earthworms on

algae has been reported so far. As a food source fungi

are most important for epigeics while bacteria are of

minor importance (Edwards & Fletcher 1988). Feeding

of earthworms on soil algae has so far been reported only

for endogeics and anecics, not epigeics (Piearce 1978;

Schmidt et al. 2016). The detailed food spectrum and

feeding behaviour of Allolobophoridella eiseni has to be

investigated in further studies.

In summary, Allolobophoridella eiseni is not a rare

species but a common member of the earthworm

communities especially in moder beech (and oak) wood

forests on acid soils in four German states located in

northern, central and southern Germany. In Scottish

heath and coniferous moor soils often only Dendrobaena

octaedra and Allolobophoridella eiseni do occur. Probably

Allolobophoridella eiseni has often been overlooked

in studies in which earthworms were collected with

traditional methods, focusing on soil and litter inhabiting

species. In fact this species is probably an important

part of the total invertebrate biomass at such habitats,

at least up to about 20 meters above ground. However,

its ecological role is difficult to quantify because pitfall

traps as well as eclector traps do not sample earthworms

per area but are activity-based. This means also that a

direct comparison between the results of hand-sorting or

chemical extraction from soil and the results of pitfall or

eclector traps is not possible.

Thus, specific sampling programs focusing on those

species inhabiting trees (i.e. not only Allolobophoridella

eiseni) should be initiated in order to clarify the

ecological role of these worms outside of the ‘normal’

habitat of earthworms. So far, examples for tree-dwelling

earthworm species are mainly known from tropical sites

(especially Latin America) but it seems possible that such

behaviour has been simply overlooked in Europe so far

due to a restriction to sampling methods which do not

cover such habitats.

In detail, further research has to clarify the food

spectrum of tree-dwelling earthworms, their migration

behaviour and their interaction with other organisms

in this very specific habitat. Similar work has, e. g.,

been done already for springtails (Shaw 2015). In fact,

at a time where research on the interactions between

below- and aboveground communities is a very hot

research topic (Sutherland et al. 2013), species such as

Allolobophoridella eiseni could play an important role

in improving our understanding of the whole terrestrial

ecosystem.

5. Acknowledgements

We thank Bernd Römbke (Karlsruhe) and Nicola

Böffinger (Frankfurt) for technical help and Martin Goßner

(Fronreute) for providing data from Bavarian sites. We are

highly indebted to our technical assistants Angela Röhner

and Carolin Kroneberger and our large team of students,

who keep the long term project running. Rüdiger Schmelz

(A Coruña) kindly checked the text linguistically. Research

was conducted in cooperation with and financially

supported by ‘Landesbetrieb Hessen-Forst’.

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