12METRANI AND BALAKRISHNANFig. 5. Temporal <strong>and</strong> spectral structure <strong>of</strong> the call<strong>in</strong>g <strong>song</strong>s <strong>of</strong> the 4 Oecanthus species represented by oscillograms <strong>and</strong> power spectra. A)O. henryi, B) O. bil<strong>in</strong>eatus, C) O. <strong>in</strong>dicus <strong>and</strong> D) O. rufescens. For each species, the uppermost oscillogram reveals the call structure (chirp/trill), the lower magnified view reveals the syllabic structure <strong>of</strong> the call <strong>and</strong> the power spectrum below shows the carrier frequency.JOURNAL OF ORTHOPTERA RESEARCH 2005, 14(1)
METRANI AND BALAKRISHNAN 13but multi-dimensional scal<strong>in</strong>g gave a far superior representation <strong>in</strong>the case <strong>of</strong> quantitative <strong>morphological</strong> <strong>characters</strong> (Table 2).In the case <strong>of</strong> 42 quantitative <strong>morphological</strong> <strong>characters</strong> (Fig.7A,B), <strong>in</strong>ternal allocation <strong>of</strong> each <strong>of</strong> the 40 <strong>in</strong>dividuals (Table 2)resulted <strong>in</strong> 100% (10 out <strong>of</strong> 10) correct species allocation <strong>of</strong> O.bil<strong>in</strong>eatus <strong>and</strong> O. <strong>in</strong>dicus, <strong>and</strong> 90% (9 out <strong>of</strong> 10) correct allocation<strong>of</strong> O. henryi with both cluster<strong>in</strong>g <strong>and</strong> MDS. O. rufescens was, however,100% correctly allocated us<strong>in</strong>g MDS whereas there was onemisallocation us<strong>in</strong>g the cluster<strong>in</strong>g algorithm. External allocation <strong>of</strong>10 new O. <strong>in</strong>dicus <strong>and</strong> O. henryi males, <strong>and</strong> 9 O. rufescens resulted<strong>in</strong> 100% correct allocation <strong>of</strong> O. <strong>in</strong>dicus <strong>and</strong> O. henryi us<strong>in</strong>g MDS(Table 2). External allocation us<strong>in</strong>g cluster<strong>in</strong>g was less successful,with only 40 to 50% correct allocation <strong>of</strong> O. <strong>in</strong>dicus <strong>and</strong> O. rufescens,<strong>and</strong> 80% correct allocation <strong>of</strong> O. henryi.In the case <strong>of</strong> the 12 qualitative <strong>morphological</strong> <strong>characters</strong> (Fig.7C,D), <strong>in</strong>ternal allocation <strong>of</strong> each <strong>of</strong> the 40 <strong>in</strong>dividuals resulted <strong>in</strong>100% correct allocation (10 out <strong>of</strong> 10) for all 4 species us<strong>in</strong>g boththe cluster<strong>in</strong>g <strong>and</strong> the MDS methods (Table 2). In external allocationalso, there was100% correct species allocation <strong>of</strong> the 3 speciesexam<strong>in</strong>ed us<strong>in</strong>g both cluster<strong>in</strong>g <strong>and</strong> ord<strong>in</strong>ation.In the case <strong>of</strong> the clusters <strong>and</strong> ord<strong>in</strong>ations obta<strong>in</strong>ed us<strong>in</strong>g 4<strong>song</strong> <strong>characters</strong> (Fig. 7 E,F), there was aga<strong>in</strong> 100% correct <strong>in</strong>ternalallocation for each <strong>of</strong> the 4 species with both methods. <strong>The</strong> <strong>song</strong>s<strong>of</strong> 10 males (<strong>of</strong> each <strong>of</strong> the 3 species O. <strong>in</strong>dicus, O. henryi <strong>and</strong> O.rufescens) that had not been used to construct the species clusterswere employed, one at a time, for external allocation <strong>of</strong> speciesidentity. <strong>The</strong> cluster<strong>in</strong>g algorithm gave 100% correct allocation (10out <strong>of</strong> 10) <strong>in</strong> the case <strong>of</strong> O. henryi <strong>and</strong> O. <strong>in</strong>dicus, <strong>and</strong> 90% correctallocation (9 out <strong>of</strong> 10) <strong>in</strong> the case <strong>of</strong> O. rufescens (Table 2). <strong>The</strong>MDS technique yielded 100% correct allocation (10 out <strong>of</strong> 10) <strong>in</strong>the case <strong>of</strong> O. henryi <strong>and</strong> O. rufescens, <strong>and</strong> 90% correct allocation<strong>of</strong> O. <strong>in</strong>dicus.In summary, both the cluster<strong>in</strong>g <strong>and</strong> ord<strong>in</strong>ation techniqueswere 90 to 100% successful <strong>in</strong> achiev<strong>in</strong>g correct species allocation(with new specimens) <strong>in</strong> the case <strong>of</strong> <strong>song</strong> <strong>and</strong> qualitative <strong>characters</strong>.In the case <strong>of</strong> quantitative <strong>morphological</strong> <strong>characters</strong>, however, theMDS was superior <strong>and</strong> gave close to 100% correct allocation <strong>of</strong> newspecimens, whereas the cluster<strong>in</strong>g algorithm performed poorly for2 <strong>of</strong> the 3 species <strong>in</strong> external allocation (Table 2).Number <strong>of</strong> <strong>characters</strong>.—In the analyses described above, the number<strong>of</strong> <strong>characters</strong> <strong>in</strong> the 3 sets to be compared (quantitative <strong>morphological</strong>,qualitative <strong>morphological</strong> <strong>and</strong> <strong>song</strong>) were unequal, evenby an order <strong>of</strong> magnitude. In order to exam<strong>in</strong>e more closely theeffect <strong>of</strong> the number <strong>of</strong> <strong>characters</strong> on the efficacy <strong>of</strong> species group<strong>in</strong>g<strong>and</strong> allocation, <strong>in</strong> the next set <strong>of</strong> analyses we varied the number <strong>of</strong>quantitative <strong>and</strong> qualitative <strong>morphological</strong> <strong>characters</strong> used.Quantitative <strong>characters</strong>.— Cluster<strong>in</strong>g <strong>and</strong> MDS analyses were carriedout us<strong>in</strong>g 26, 12 <strong>and</strong> 4 r<strong>and</strong>omly picked quantitative <strong>morphological</strong><strong>characters</strong> from the total set <strong>of</strong> 42. This was repeated 10 times foreach <strong>of</strong> the sets. <strong>The</strong> results (<strong>in</strong> the form <strong>of</strong> one exemplar from eachset) are graphically illustrated <strong>in</strong> Fig. 8. A visual <strong>in</strong>spection suggestedthat the goodness <strong>of</strong> the clusters <strong>in</strong> both algorithms deterioratedwith a decrease <strong>in</strong> the number <strong>of</strong> <strong>characters</strong> used.To exam<strong>in</strong>e this more quantitatively, we calculated 1) the copheneticcorrelation coefficient r csbetween the orig<strong>in</strong>al distancematrix <strong>and</strong> the representation as a result <strong>of</strong> cluster<strong>in</strong>g or ord<strong>in</strong>ation<strong>and</strong> 2) the co-phenetic correlation coefficient between matricesrepresent<strong>in</strong>g 2 clusters or ord<strong>in</strong>ations, r c1c2(Sneath & Sokal 1973),<strong>of</strong> which one (the reference) was always the cluster or ord<strong>in</strong>ationthat resulted from the analysis <strong>of</strong> 42 quantitative <strong>morphological</strong><strong>characters</strong>. <strong>The</strong> mean value <strong>of</strong> r cs<strong>and</strong> r c1c2(based on 10 runs <strong>of</strong>cluster<strong>in</strong>g <strong>and</strong> ord<strong>in</strong>ation) was calculated <strong>in</strong> the case <strong>of</strong> 26, 12 <strong>and</strong>4 quantitative <strong>morphological</strong> <strong>characters</strong>.<strong>The</strong> results, summarised <strong>in</strong> Table 3, showed that the averagevalue <strong>of</strong> both r cs<strong>and</strong> r <strong>in</strong>creased with the number <strong>of</strong> r<strong>and</strong>omlyc1c2picked <strong>characters</strong> <strong>in</strong> both cluster<strong>in</strong>g <strong>and</strong> ord<strong>in</strong>ation. In other words,the fidelity with which the cluster<strong>in</strong>g or ord<strong>in</strong>ation represented theorig<strong>in</strong>al distance matrix <strong>in</strong>creased with the number <strong>of</strong> <strong>characters</strong>. <strong>The</strong>MDS technique was, however, consistently superior to the clusteranalysis <strong>in</strong> its fidelity to the orig<strong>in</strong>al distance matrix (Table 3). <strong>The</strong>clusters or ord<strong>in</strong>ations also became progressively more similar tothe pattern produced by 42 <strong>characters</strong>, with r c1c2<strong>in</strong>creas<strong>in</strong>g froman average <strong>of</strong> 0.64 for 4 <strong>characters</strong> to 0.95 for 26 <strong>characters</strong> <strong>in</strong> thecase <strong>of</strong> cluster<strong>in</strong>g <strong>and</strong> from 0.75 to 0.97 <strong>in</strong> the case <strong>of</strong> MDS (Table3). In addition, the variation <strong>in</strong> both r cs<strong>and</strong> r c1c2decreased (shownTable 2. Internal <strong>and</strong> external allocation <strong>of</strong> <strong>in</strong>dividuals after cluster<strong>in</strong>g <strong>and</strong> ord<strong>in</strong>ation us<strong>in</strong>g different types <strong>of</strong> <strong>characters</strong>Type <strong>of</strong> characterUPGMA cluster analysisO. bil<strong>in</strong>eatus O. henryi O. <strong>in</strong>dicus O. rufescens rcsQuantitative <strong>morphological</strong> (n = 42) 10/10 9/10 (8/10) 10/10 (4/10) 9/10 (4/9) 0.86Qualitative <strong>morphological</strong> (n = 12) 10/10 10/10 (10/10) 10/10 (10/10) 10/10(9/9) 0.98Song (n = 4) 10/10 10/10 (10/10) 10/10 (10/10) 10/10 (9/10) 0.99Multi-dimensional scal<strong>in</strong>gQuantitative <strong>morphological</strong> (n = 42) 10/10 9/10 (10/10) 1010 (10/10) 10/10 (8/9) 0.98Qualitative <strong>morphological</strong> (n = 12) 10/10 10/10 (10/10) 10/10 (10/10) 10/10 (9/9) 0.98Song (n = 4) 10/10 10/10 (10/10) 10/10 (9/10) 10/10 (10/10) 0.99Numbers <strong>in</strong>dicate number <strong>of</strong> correctly allocated <strong>in</strong>dividuals for <strong>in</strong>ternal allocationNumbers <strong>in</strong> brackets <strong>in</strong>dicate number <strong>of</strong> correctly allocated <strong>in</strong>dividuals for external allocationNumber <strong>of</strong> <strong>in</strong>dividuals <strong>of</strong> each species used for <strong>in</strong>ternal allocation = 10Number <strong>of</strong> <strong>in</strong>dividuals used for external allocation with <strong>morphological</strong> <strong>characters</strong>: O. henryi = 10, O. <strong>in</strong>dicus = 10, O. rufescens = 9Number <strong>of</strong> <strong>in</strong>dividuals used for external allocation with <strong>song</strong> <strong>characters</strong>: O. henryi = 10, O. <strong>in</strong>dicus = 10, O. rufescens = 10r cs =cophenetic correlation coefficient between the orig<strong>in</strong>al distance matrix <strong>and</strong> the cophenetic distance matrix derived from the cluster or ord<strong>in</strong>ationJOURNAL OF ORTHOPTERA RESEARCH 2005, 14(1)
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