Research Article |
Corresponding author: Bernhard Seifert ( bernhard.seifert@senckenberg.de ) Academic editor: Dominique Zimmermann
© 2019 Bernhard Seifert.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Seifert B (2019) The Rubens morph of Formica exsecta Nylander, 1846 and its separation from Formica fennica Seifert, 2000 (Hymenoptera, Formicidae). Deutsche Entomologische Zeitschrift 66(1): 55-61. https://doi.org/10.3897/dez.66.34868
|
A study of numeric morphology-based alpha-taxonomy (NUMOBAT) considering the species Formica exsecta Nylander, 1846 and F. fennica Seifert, 2000 was performed in 166 nest samples with 485 worker individuals originating from 117 localities of the Palaearctic west of 59°E. The presence of intraspecific pilosity dimorphism is shown for F. exsecta. The setae-reduced phenotype, termed the Rubens morph, shows a frequency of about 25%, and the more abundant setae-rich phenotype, termed the Normal morph, one of 75%. The frequency of nests containing workers of both phenotypes is 15.5% in 58 samples from Denmark, Sweden, and Finland. Applying the DIMORPH test of
cryptic species, dimorphism, numeric taxonomy, parabiosis
The distributional range of Formica exsecta Nylander, 1846 covers the Palaearctic from Iberia to Kamchatka, includes the submeridional, temperate and boreal zones in the horizontal scale, and extends from the planar to the subalpine zone in the vertical scale (
To have an improved separation between the Formica exsecta morphs and between the Rubens morph of F. exsecta from F. fennica, the materials of this study were restricted to the Palaearctic west of 59°E, that is, west of the Ural Mountains. NUMOBAT data were recorded in 166 nest samples and 485 worker individuals, the majority of which is deposited in the collection of Senckenberg Museum of Natural History Görlitz. This material listed below in the following sequence and format: site, date in the yyyy.mm.dd format, field sample number “field No” which is found on the mounted specimens [latitude and longitude in decimal format, meters above sea level]. The accuracy of coordinates is proportional to the number of decimal points and “xx” in the sampling date sequence mean missing data. In some samples without any direct or derived information of date, the assumed period is given and the collector is named if known.
A total of 152 nest samples with 431 workers were investigated.
Austria: Brunau, 2001.09.xx [47.23, 10.85, 700]; Fernpass, 1994.07.04, no. 20 [47.40, 10.90, 1420]; Gilfert, Lafaster-Alm, 1995.10.22 [47.26, 11.76, 1758]; Großglockner, Franz-Josephs-Höhe, 1968.xx.xx [47.075, 12.751, 2369]; Großglockner, Glocknerhaus, 1994.06.20 [47.070, 12.769, 2200]; Gschnitz, Sandertal, 1995.09.24 [47.00, 11.40, 1700]; Gschnitz, Schatthang, 1995.09.24 [47.00, 11.40, 1900]; Gschnitz, Blockfeld, 1995.09.24 [47.00, 11.40, 1900]; Kitzbühel, Bischof, 1994.08.22 [47.405, 12.512, 2000]; Kleiner Gamsstein, 1995.10.22 [47.733, 14.467, 1100]; National Park Kalkalpen, 2011.08.05 [47.750, 14.438, 990]; Pottenbrunn-3 km SSW, 1994.05.12, no. 043 [48.215, 15.718, 330]; Rofan, 1994.07.07, no. g23 [47.45, 11.78, 2000]; Seetaler Alp, Zirbitzkogel, 1971.09.04 [47.06, 14.55 2000]; Spitz-15 km W, Jauerling, 1990.07.05 [48.353, 15.332, 700]; Vikartal, 1995.10.08 [47.20, 11.45, 1500]. Bulgaria: Rhodopes: “Betova” [site not identifiable], 1985.07.03 [42?, 24.5?, 1300]; Rhodopes: Pamporovo, 1975.07.20 [41.61, 24.67, 1400]; Rila: Borovec, 1977.08.01 [42.26, 23.61, 1300]; Rila: Borovec, 1988.06.16 [42.26, 23.61, 1900]. Denmark: Jutland, Rye, 1986.08.xx [56.08, 9.73, 77]. Finland: Broända, 1996.07.07, no. 27, no. 130 [60.11, 24.27, 30]; Jyväskylä, Kypäramäki, 1998.06.01 [62.24, 25.70, 140]; Järajärvi-S, 2002.07.23 no. 039 [69.641, 29.046, 102]; Järajärvi-S, 2002.07.23 no. 040 [69.641, 29.045, 101]; Järajärvi-S, 2002.07.23 no. 041 [69.642, 29.045, 101]; Järajärvi-S, 2002.07.23 no. 042, no. 044 [69.642, 29.046, 100]; Kiannanniemi, 2002.07.19, no. 018 [65.165, 29.105, 207]; Kiiminki-26 km ENE, 1996.07.15, no. 146 [65.208, 26.325, 120]; Käylä-2 km NE, 1996.07.17, no. 147 [66.320, 29.170, 250]; Käylä-3 km E, no. 113, no. 159 [66.310, 29.203, 250]; Köyliö, 1999.06.25 [61.117, 22.300, 70]; Puhos-6.5 km WNW, 1996.07.13, no. 114 [62.107, 29.793, 97]; Renko-13 km WSW, 1996.07.11, no. 19 [60.836, 24.067, 136]; Sodankylä-26 km NNE, 1996.07.18, no. 55 [67.64, 26.74, 205]; Sodankylä-33 km N, 2002.07.21, no. 029, no. 031 [67.707, 26.749, 208]; Tammela-9 km ENE, 1996.07.11 [60.83, 23.93, 120]; Tronsböle-0.2 km NE, Oby, 2015.05.07, no. A, no. B [59.940, 23.198, 20]; Utajärvi-2 km NE, no. 120 [64.728, 24.426, 80]. France: Mt. Canigou, pre 1918, type F. dalcqi [42.51, 2.45, 2000]; Mt. Canigou, pre 1930 (leg. Weiss) [42.51, 2.45, 2200]; Refuge des Besines, 1998.09.17, no. 016 [42.604, 1.868, 2100]. Germany: Althüttendorf, 1985.05.07 [52.96, 13.80, 71]; Canthnitz-0.7 km E, 1997.08.23, no. 220 [53.376, 13.394, 103]; Dabelow, 1982.06.01 [53.248, 13.198, 64]; Dallgow-S, 1996.08.03 [52.52, 13.06, 41]; Eberswalde, 1987.06.12 [52.83, 13.79, 31]; Eberswalde-2.4 km E, 1997.08.21 [52.82, 13.85, 66]; Eberswalde-5 km N, 1995.07.10 [52.89, 13.88, 38]; Eberswalde-Buchholz, 1985.05.07 [52.88, 13.76, 70]; Eberswalde-Finow, 1987.04.12 [52.84, 13.73, 35]; Federsee: Wildes Ried, 1990.09.xx [48.045, 9.648, 583]; Federsee: Wildes Ried, 1991.05.xx [48.045, 9.648, 583]; Geesow, 1987.08.03 [53.239, 14.388, 25]; Meseberg, 1982.08.30 [52.95, 13.10, 50]; Müritzhof, 1988.07.27 [53.45, 12.74, 70]; Carwitz, NSG Hauptmannsberg, 2000.04.22, no. 014, no. 016, no. 017, no. 019, no. 024 [53.31, 13.455, 115]; Neulöwenberg 1982.06.xx [52.90, 13.19, 67]; Oberhersdorf-2 km ENE, 1991.09.04 [50.180, 6.542, 580]; Ödenwaldstetten, 1991.05.19, no. 19 [48.35, 9.39, 750]. Italy: Abetone, pre. 1920 [44.143, 10.666, 1400]; Abetone, Seletta, 1960.07.15 [44.132, 10.644, 1700]; Apennino Modenese: Le Pozze, 1941.07.26, [44, 11, 1000, guess]; Bosco di Corniglio, 1985.08.xx [44.44, 10.04, 880]; Corvara: Colfosco, 1993.08.22 [45.56, 11.86, 1900]; Monte Cimone, Lago Ninfa, 1959.xx.xx, no. 55–57 [44.21, 10.72, 1500]; Praccia, 1890.07.xx, type F. etrusca [44.061, 10.911, 750]; Pejo-6 km N, Stelvio NP, 2004.06.16, no. 18 [46.411, 10.688, 2400]; Toscanian Alps: Giulia (leg. Wolf) pre 1945 [44,10,1000, guess]. Netherlands: Bergen, 1994.09.13 [52.670, 4.677, 11]. Norway: Alta-9.5 km S, 2015.07.10, no. 1, no. 2 [69.911, 23.081, 90]; Gjoktbukmyra, 2016.07.11, no. 4 [69.147, 29.207, 64]; Hedmark: Dalholen, 1993.06.28 [62.191, 9.746, 820]; Klingenberg, 2015.08.20, no. 6 [61.017, 11.855, 493]; Klingenberg-E, 2012.07.13, no. 93 [61.001, 12.060, 460]; Klingenberg-Ulva, 2012.07.13, no. 92 [61.001, 12.059, 462]; Osen: Drageid: Seter-4.8 km E, 2012.04.29 [64.392, 10.589, 45]; Osen: Drageid, 2015.08.24, no. 1–3 [64.392, 10.589, 55]; Osen: Drageid, 2016.08.23, no. 3 [64.391, 10.590, 59]; Oyermoen, 2012.06.27, no. 71 [60.248, 12.442, 300]; Tysil: Torberget, 2015.08.21, no. 4, no. 5 [61.105, 12.019, 528]; Tysil: Torberget, 2016.07.23, no. 1, no. 2 [61.105, 12.019, 528]. Russia: Kormovische, 2001.xx.xx, no. U79 [56.83, 57.95, 250]; Svenigorod, 1985.08.xx, no. 623 [55.70, 36.72, 150]; Voronesh Zapovednik, 1962.08.29, no. 221, type F. nemoralis [51.809, 39.446, 130]. Slovenia: Loibl Pass-5 km S, 1994.07.11, no. g10, no. 12 [46.404, 14.277, 700]. Spain: Camprodon-10 km NW, 1994.07.13 [42.401, 2.304, 1600]; Sierra de Guadarrama, 2009.10.16 [40.823, -3.960, 1824]. Sweden: Aaland, 1998.xx.xx, no. S60 [60.23, 19.95, 20]; Abisko, 1951.07.xx [68.50, 18.66, 500]; Andrarum, 1992.06.09, no. g4, no. g17 [55.708, 13.966, 115]; Ange-WSW, 2002.08.03, no. 029–032 [62.422, 15.000, 269]; Arvidsjaur-Aljeplog, 2002.07.29, no. 013, no. 014 [65.926, 18.311, 464]; Attonträsk-4 km SW, 1996.07.29, no. 109, no. 125 [64.401, 18.004, 471]; Attoträsk-6 km NE, 1996.07.28, no. 49, no. 76, no. 137, no. 141 [64.461, 18.153, 430]; Degeberga- 6 km SSW, 1992.06.09, no. g89 [55.784, 14.045, 125]; Falkenberg, 2000.xx.xx [56.92, 12.49, 32]; Kalix, 2000.xx.xx, no. S96, no. S100, no. S101 [65.84, 23.10, 7]; Orsa-45 km N, 2002.08.04, no. 036, no. 037 [61.407, 14.819, 480], Orsa-45 km N, 2002.08.04, no. 039 [61.409, 14.821, 476]; Storuman, 2002.07.31, no. 018 [64.924, 17.034, 422]; Storuman, 2002.07.31, no. 019 [64.923, 17.033, 423]; Sweg, 2002.08.04, no. 034 [62.140, 13.984, 378]; Upland: Hallnäs, 1998.xx.xx, no. S75 [60.53, 17.87, 10]; Öland: Böda, 1992.06.14 [57.250, 17.06, 9]; Öland: Borgholm Slott, 2000.10.08, no. 008–010 [56.870, 16.640, 60]; Östernoret-3 km SW, 1996.07.29, no. 71, no. 126 [64.071, 17.290, 320]. Switzerland: Alp La Schera, 1998.07.26, no. 51 [47.648, 10.194, 2080]; Valle Fermaur: Apples, pre 1874, type F. rubens [46.550, 6.433, 622]; La Punt-3.7 km NW, no. 58, no. 106 [46.588, 9.900, 2150]; S-Scharl-0.5 km S, 1998.07.27, no. 184 [46.713, 10.336, 1900]; S-Scharl-0.8 km S, 1998.07.27, no. 243 [46.710, 10.334, 2100]; S-Scharl-0.9 km S, 1998.07.27, no. 182 [46.709, 10.333, 2215]; S-Scharl-2.6 km SSE, 1998.07.27, no. 146 [46.697, 10.350, 2140]; S-Scharl-2.6 km SSE, 1998.07.27, no. 247 [46.697, 10.347, 2175]; Stabelchod, 1998.07.28, no. 81 [46.661, 10.241, 1940]; Stabelchod, 1998.07.28, no. 174 [46.665, 10.243, 1990]; Stabelchod- 1 km W, 1998.07.28, no. 172 [46.662, 10.224, 1880]; Ticino: Piora, 1981.07.22 [46.544, 8.686, 1930]. Turkey: Gerede, 1976.02.27 [40.810, 32.192, 1600].
A total of 14 nest samples with 54 workers were investigated.
Azerbaijan: Ilisu, 2006.06.03, no. 24 [41.457, 47.063, 1706]. Finland: Iisalmi Kotikylä, 1998.07 [63.450, 27.167, 100]; Iisalmi Kotikylä, 2009.07.24 [63.450, 27.167, 100]; Ilomantsi, Maukkula, pre 1996 (leg. Saaristo) [62.62, 30.84, 170]; Luhanpää-1.42 km NE, 1999.07.07, no. 273 [61.058, 25.050, 130]; Luhanpää-1.42 km NE, 2001.07.22, no. 1, no. 2 [61.058, 25.050, 130]; Puhos-6.5 km WNW, 1996.07.13, no. 86, no. 105, no. 119 (type F. fennica) [62.108, 29.800, 100]; Puhos-6.5 km WNW, 2002.07.19, no. 013–015 [62.108, 29.800, 100]. Georgia: Schenako, 1985.08.01 [42.732, 45.662, 1600].
Stereomicroscopic equipment and measurement procedures were as given in
NUMOBAT data were recorded in the primary characters CS, CL, CW, ClySet, ClyPub, EyeHL, F2L, F3L, nCox, nHTfl, nMet, nOce, OceD, SL, sqPDG, sqPDO, TERG, and T3f; the recording rules are explained in
Hypotheses on phenotype dimorphism within the F. exsecta sample were formed by a Two-Step Cluster Analysis (TSCA). The TSCA was run with automatic determination of the number of clusters using the SPSS 15.0 software package. The first step of analysis is construction of a Cluster Features (CF) tree which provides a capsule summary of the data file. The second step is grouping the leaf nodes of the CF tree using an agglomerative clustering algorithm which produces a range of solutions which are then compared using Schwarz’s Bayesian Criterion to determine the “best” number of clusters. The hypothesis provided by the TSCA was checked and corrected by a single run of a linear discriminant analysis (LDA). LDA, Principal Component analysis (PCA), ANOVA and X² tests were run with the SPSS 15.0 software package. The DIMORPH test was performed according to
Nest samples of F. exsecta containing only worker individuals of the setae-reduced Rubens morph are under increased risk of being confused with F. fennica. In order to demonstrate a clear species separation, these samples were run together with those of F. fennica in different forms of exporatory data analyses using nest centroids as input data (NC clustering;
Standard air temperature (TAS) in °C of sampling sites 2 m above ground can be used as a rough approximation of the thermal niche component (
The analysis of phenotype variance was restricted to the characters CS, CL/CW, SL/CS, ClySet, ClyPub, nOce, OceD/CS, EyeHL, sqPDO, sqPDG, TERG, nCox, nHTFl, and nMet because the full set of characters was not available for all Western Palaearctic samples. Yet, three of the four excluded characters (F2L/CS, F3L/CS, and F2L/F3L) did not contribute to morph separation (Table
D(7) = 5.098*SL/CS + 1.609*ClySet-0.044*EyeHL-0.191*sqPDO-0.45*TERG + 0.100*nCox+0.064*nMet-7.9705.
Morphometrics of worker individuals of Formica fennica and the two pilosity morphs of F. exsecta. Data are given as arithmetic mean ± standard deviation [lower extreme, upper extreme]; n = number of individuals. The columns with data of an univariate ANOVA test (F values, significance levels p, and degrees of freedom df2) are placed between the columns of the compared entities. F values of most discriminative characters are given in heavy type.
F. exsecta Normal morph (n=288) | ANOVA F, p df2 | F. exsecta Rubens morph (n=143) | ANOVA F, p df2 | F. fennica (n=54) | |
---|---|---|---|---|---|
CS [µm] | 1390 ± 81 | 1.66, 0.198 | 1397± 83 | 65.03, 0.000 | 1287 ± 93 |
[1143,1586] | 429 | [1145,1608] | 195 | [1050,1468] | |
CL/CW | 1.045 ± 0.023 | 15.50, 0.000 | 1.054 ± 0.020 | 18.52, 0.000 | 1.068 ± 0.021 |
[0.983,1.119] | 429 | [1.009,1.105] | 195 | [1.019,1.118] | |
SL/CS | 1.028 ± 0.022 | 9.91, 0.002 | 1.020 ± 0.023 | 0.09, 0.762 | 1.022 ± 0.026 |
[0.966,1.085] | 429 | [0.965,1.071] | 195 | [0.962,1.084] | |
EyeHL | 27.2 ± 6.9 | 0.89, 0.347 | 26.5 ± 8.0 | 5.17, 0.024 | 23.9 ± 2.3 |
[0.0,60.3] | 429 | [16.1,44.8] | 195 | [20.7,27.0] | |
TERG | 1.03 ± 0.16 | 227.18, 0.000 | 1.92 ± 0.98 | 117.02, 0.000 | 3.48 ±0.64 |
[1.0,2.0] | 429 | [1.00,4.00] | 195 | [3.0,6.0] | |
nCOX | 9.63 ± 2.99 | 399.87, 0.000 | 4.00 ± 2.26 | 97.07, 0.000 | 0.89 ±0.88 |
[2.5,18.5] | 429 | [0.5,13.0] | 195 | [0.0,3.0] | |
nHTFL | 9.45 ± 1.89 | 69.28, 0.000 | 7.93± 1.65 | 6.69, 0.010 | 7.22 ±1.93 |
[5.1,15.5] | 429 | [3.8,13.1] | 195 | [4.2,13.9] | |
nMET | 2.26 ± 2.15 | 100.89, 0.000 | 0.37 ± 0.75 | 13.09, 0.000 | 0.00 ± 0.00 |
[0.0,10.0] | 429 | [0.0,3.7] | 195 | [0,0.0] | |
sqPDO | 5.38 ± 0.98 | 79.53, 0.000 | 6.43 ± 1.44 | 2.51, 0.115 | 6.77 ± 1.04 |
[3.21,8.91] | 429 | [3.74,13.40] | 195 | [4.52,9.92] | |
sqPDG | 6.87 ± 1.20 | 12.64, 0.000 | 7.31 ± 1.36 | 2.35, 0.127 | 7.61 ± 0.56 |
[3.93,9.84] | 429 | [4.33,10.73] | 195 | [6.58,8.71] | |
ClySet | 4.09 ± 0.56 | 1206.1, 0.000 | 2.17 ± 0.48 | 32.46, 0.000 | 1.72 ± 0.53 |
[2.0,5.0] | 429 | [1.0,3.0] | 195 | [1.0,3.0] | |
ClyPub | 3.13 ± 1.04 | 0.70,0.404 | 3.01 ± 1.25 | 26.23, 0.000 | 2.07 ± 0.82 |
[0.8,6.5] | 429 | [0.5,6.5] | 195 | [0.5,4.3] | |
nOce | 2.16 ± 0.56 | 95.59, 0.000 | 1.57 ± 0.65 | 195.10, 0.000 | 0.24 ± 0.42 |
[0.7,6.0] | 429 | [0.0,4.0] | 195 | [0.0,1.7] | |
OCED /CS | 0.188 ± 0.010 | 0.00, 0.97 | 0.188 ± 0.011 | 20.27, 0.000 | 0.180 ± 0.010 |
[0.155,0.210] | 429 | [0.161,0.217] | 195 | [0.156,0.198] | |
T3f | 0.97 ± 0.15 | 34.46, 0.000 | 0.77 ± 0.41 | 144.19, 0.000 | 0.06 ± 0.22 |
[0.00,1.00] | 301 | [0.00,1.00] | 182 | [0.00,1.00] | |
FL2/FL3 | 0.987 ± 0.040 | 3.03, 0.084 | 0.979 ± 0.040 | 20.60, 0.000 | 1.004 ± 0.033 |
[0.896,1.077] | 142 | [0.885,1.085] | 144 | [0.938,1.094] | |
FL2/CS | 13.57 ±0.59 | 4.57, 0.034 | 13.37 ±0.53 | 0.30, 0.586 | 13.31 ±0.68 |
[12.43,14.77] | 142 | [12.08,14.63] | 144 | [11.98,15.21] |
Individuals with D(7) <0 were classified as Rubens morph and those with larger values as Normal morph. This discriminant classified 94.9% of the 431 specimens with posterior probabilities > 0.90 (the recognition threshold used in the DIMORPH test, see below). Figure
Morph composition in type series of taxa synonymized with Formica exsecta Nylander, 1846. D(7) is the discriminant value considering seven phenotypic characters, p(Norm) and p(Rube) are the posterior probability for the Normal and Rubens morph. Data indicating the Normal morph are shaded in grey.
Taxon; site; specimen no. | D(7) | p(Norm) | p(Rube) |
---|---|---|---|
F. exsecta rubens Forel, 1874; Apples; no. 1 | -1.692 | 0.0004 | 0.9996 |
F. exsecta rubens Forel, 1874; Apples; no. 2 | -2.582 | 0.0000 | 1.0000 |
F. exsecta rubens Forel, 1874; Apples; no. 3 | -0.665 | 0.0364 | 0.9636 |
F. exsecta rubens Forel, 1874; Apples; no. 4 | -2.769 | 0.0000 | 1.0000 |
F. exsecta etrusca Emery, 1909; Praccia; no. 1 | -2.396 | 0.0000 | 1.0000 |
F. exsecta etrusca Emery, 1909; Praccia; no. 2 | -2.107 | 0.0001 | 0.9999 |
F. exsecta etrusca Emery, 1909; Praccia; no. 3 | -1.862 | 0.0002 | 0.9998 |
F. exsecta etrusca Emery, 1909; Praccia; no. 4 | -1.945 | 0.0001 | 0.9999 |
F. exsecta etrusca Emery, 1909; Praccia; no. 5 | -0.3925 | 0.1114 | 0.8886 |
F. dalcqi Bondroit, 1918; Mount Canigou; no. 1 | 2.256 | 0.9999 | 0.0001 |
F. dalcqi Bondroit, 1918; Mount Canigou; no. 2 | 0.568 | 0.8954 | 0.1046 |
F. dalcqi Bondroit, 1918; Mount Canigou; no. 3 | 3.414 | 1.0000 | 0.0000 |
F. nemoralis Dlussky, 1964; Voronesh Zapovednik; no. 1 | -3.134 | 0.0000 | 1.0000 |
F. nemoralis Dlussky, 1964; Voronesh Zapovednik; no. 2 | -2.601 | 0.0000 | 1.0000 |
F. nemoralis Dlussky, 1964; Voronesh Zapovednik; no. 3 | -2.939 | 0.0000 | 1.0000 |
F. nemoralis Dlussky, 1964; Voronesh Zapovednik; no. 4 | -2.874 | 0.0000 | 1.0000 |
F. nemoralis Dlussky, 1964; Voronesh Zapovednik; no. 5 | -2.554 | 0.0000 | 1.0000 |
F. nemoralis Dlussky, 1964; Voronesh Zapovednik; no. 6 | -1.684 | 0.0004 | 0.9996 |
F. nemoralis Dlussky, 1964; Voronesh Zapovednik; no. 7 | 1.082 | 0.9880 | 0.0120 |
F. nemoralis Dlussky, 1964; Voronesh Zapovednik; no. 8 | -3.087 | 0.0000 | 1.0000 |
F. nemoralis Dlussky, 1964; Voronesh Zapovednik; no. 9 | -2.023 | 0.0001 | 0.9999 |
Within 152 nest samples from the Palaearctic west of 59°E, 104 samples contained only the Normal morph, 28 only the Rubens morph and 20 a mixture of both the Normal and Rubens morph. This figure of 13.2% of mixed nests already indicates heterospecificity to be most unlikely. Yet, checking the alternatives intraspecific dimorphism versus heterospecificity by the DIMORPH test is problematic considering the huge geographic area and heterogenous sampling philosophies of different collectors. Among the conditions allowing to run the DIMORPH test are panmictic behaviour and random sampling, i.e., no preference to collect certain phenotypes (
The only coherent geographic area with random, unbiased sampling and evaluation of F. exsecta samples included Finland, Sweden, and northern Denmark, largely based on the collecting activity of the Senckenberg Museum of Natural History Görlitz. Selecting this area makes also sense because the geographic reference is then well comparable with that in the study of
The DIMORPH test was run for this area with the following basic data and parameters. Among 58 nest samples, 42 samples contained only the Normal morph, seven samples only the Rubens morph, and nine samples a mixture of both morphs. These data are based on a recognition threshold of p>0.90 in the LDA considering seven characters. Of the 157 individuals in the data set, 74.5% belonged to the Normal morph and 25.5% to the Rubens morph. Supposing a dominant-recessive inheritance and the Hardy-Weinberg model of population genetics, this would result in a frequency of the recessive ‘allele’ of 0.505 if Rubens is recessive and of 0.863 if Normal is recessive. Using these parameters, the DIMORPH test was run for both assumptions with 500 repeats each and the data were averaged. The clear results are presented in Table
DIMORPH test comparing 58 observed within-nest phenotype compositions with four prediction models. Agreement of observation and predictions was tested by Fisher’s exact test (p) and the Chi-squared test (X², p).
within-nest phenotype composition | observed | prediction heterospecificity | prediction intraspecific dimorphism | ||
---|---|---|---|---|---|
parabiosis | temporary social parasitism | permanent social parasitism | |||
only Rubens | 7 | 8.20 | 2.08 | 0.00 | 8.41 |
Rubens + Normal | 9 | 0.58 | 0.09 | 1.16 | 12.20 |
only Normal | 42 | 49.22 | 55.84 | 56.84 | 37.39 |
Fisher’s p | 0.017 | 0.0004 | 0.0001 | 0.659 | |
X², p | 8.07, 0.018 | 13.4, 0.001 | 15.28, 0.0001 | 0.88, 0.547 |
Nest samples of Formica exsecta containing only worker individuals of the Rubens morph are at increased risk of being confused with F. fennica. Only these critical samples, but this time originating from the whole of the Western Palaearctic and having T3f data available, were included in the following analyses. These were 21 nest samples of the Rubens morph with 82 workers and 14 samples of F. fennica with 54 workers.
In first analytic step all 18 NUMOBAT characters were used unselectively as input and for the exploratory data analyses NC-Ward, NC-part.hclust, and NC-NMDS-k-means. After running samples with classifications disagreeing between the different methods as wild cards, NC-Ward clustering and NC-part.hclust both showed a classification error of 0% with the latter exposing two samples as outliers (=5.7%), whereas NC-NMDS-k-means showed an error of 5.7%. NC-part.kmeans was not able to confirm the existence of two clusters for the complete unselected character set.
Accepting the former hypotheses, the character set was reduced by a stepwise LDA to the eight characters CS, CL/CW, ClySet, nOce, sqPDG, nCox, T3f, and F2L/F3L. Under this setting, all four NC-clustering algorithms achieved a classification error of 0% with NC-part.hclust exposing two samples (5.7%) as outliers (Fig.
Three exploratory and a hypothesis-driven data analysis using nest centroids (NC) as input data. Evaluated were 21 nest samples of Formica exsecta containing only Rubens morph workers (grey bars right) and 14 nest samples of F. fennica (textured grey bars left). The classifications of NC-Ward and NC-part.kmeans coincide completey whereas NC-part.hclust is also in general agreement but exposes two outlier samples (black bar).
Data on zoogeography and climate niche do also not support the presence of F. fennica in Norway. Since F. fennica apparently does not spread north to the boreal zone and does not elevate to the subalpine zone (
Many thanks are given to Igor Antonov, Volker Assing, Peter Boer, Rolf Franke, Florian Glaser, Anya Goropashnaya, Alina Kupyanskaya, Wolfgang Münch, Frode Odegaard, Andreas Schulz, Roland Schultz, Jouni Sorvari, Uwe Sörensen, Dieter Stöckel, Martin Suvak, Jürgen Trettin, Kari Vepsäläinen, Bernd Wesenigk-Sturm, Seichi Yamane, and Lothar Zerche for donating samples. I also wish to thank two anonymous referees for useful comments on the manuscript, Robert Forsyth for careful copyediting and Dominique Zimmermann for straightforward handling of the submission and editing process.